Crime scene investigators, forensic scientists, medical examiners, and police officers

We know that fiction alters many of the aspects relating to the analysis of physical evidence during an investigation. First of all it enhances the importance of this analysis, when in reality most of the time the physical evidence points to very few conclusive results for the identification of the culprit.

Second, timings do not match the real ones. Downtime is not fun, so in fiction everything happens very quickly, just a few minutes or seconds to find a match, so the culprit is identified in a day (in TV series), or in a few days (in films and novels).

Even the technology is far from the real one. Apart from the representation of science fiction equipment, that is to say that they don’t exist (yet), forensic science laboratories are always described as extremely modern and that they can rely on the latest technologies on the market, moreover they have a large staff and much time to devote to cases, without any backlog.

In reality funding for these labs are never so abundant, the staff is not enough to keep up with the crimes and then the backlog is the norm, becoming one of the main reasons why the resolution of cases can take months or years, if they are ever solved.

In addition, some laboratories may even be absent in the territory where the crime took place, therefore the exhibits may be sent elsewhere, making the process even slower. For example, in May 2016 I had the opportunity to visit one of the headquarters of Polizia di Stato (Italian police) in my city, Cagliari (the capital of Sardinia), where I was also briefly explained the role of the Polizia Scientifica (police forensics department; not to be confused with RIS, the Department of Forensics Investigations, which is part of Carabinieri and does a similar job). And I discovered that there is no biological laboratory in Cagliari, so any DNA analysis is made in Rome. Finding a source of DNA in the physical evidence is quite rare and, fortunately, violent crimes are anything but common here, so if you think about it all that has a certain logic, but considering the geographical problem (I live on an island) and the amount of work that certainly already exists in the laboratories in Rome, this isn’t an ideal situation.

This in itself would represent enough a motivation to keep me from set one of my books in my city (besides the fact that there had never been serial killers here, in the modern sense of the term).

Finally, you must consider the evaluation that this work will get in court. We know that the CSI effect may give the impression that the cases are solved, and the culprits are convicted if there is sufficient physical evidence, but in fact in most situations other types of evidence determine the outcome of a trial.

But there is another aspect that is represented in a distorted way in fiction, and that deals with forensic science: the various roles of the people involved in investigations.

In fiction, we see the same people collecting evidence on a crime scene, analysing it in the laboratory, identifying suspects, interrogating them, the witnesses and victims (if the latter aren’t dead!), and even carrying out the arrests.

The reality is often different. There are the so-called crime scene investigators, who collect evidence at the scene. Then there are the forensic scientists who analyse them and possibly a medical examiner, in the case of a murder. Instead, the identification of the suspects, interrogations, and arrests are carried out by police officers and detectives. Forensic experts and medical examiners, then, may come into play in the courtroom to explain the results of their analysis of physical evidence.

This compartmentalisation, as well as having an organisational purpose (each one specialises in one aspect, thus providing better performance), is important to keep a certain objectivity during an investigation. In certain geographical areas the separation between the various roles is less clear, but is total in others. Sometimes, as it often happens in the UK, crime scene investigators and/or forensic experts may not be police officers.

At the same time, however, all these people interact with each other; they shall consult, because if this didn’t happen there would be a reduction in efficiency. In short, they try to find the right balance that yields the best result. Then this, contrary to what is observed in fiction, may come, or worse, be wrong, because these are always people who can make mistakes.

Therefore, there is a specific terminology that in fiction isn’t used or is simplified, because the real one tends to change with the country or simply is too long or abstruse to be used in fiction.

A classic example is offered by the terms anatomopathologist, medical examiner, and coroner. They are three different things that often coincide in fiction and can even do it in reality, but it isn’t always so. The anatomopathologist is a specialist that identifies and analyses tissue and organ alterations due to illness. Typically, they work on the living, not the dead. However, they may be involved in an investigation or become a coroner, for their specialisation is particularly suitable for determining the cause of death or other injuries in the body of a victim.

The medical examiner is, in short, the person in charge of the autopsies. They should not necessarily be specialised in anatomical pathology. It is a kind of career where doctors who have specialised in something else can converge. This reminds me of an example in fiction: “Body of Proof”, where the protagonist is a neurosurgeon who because of an accident can no longer exercise, and then she starts working as a medical examiner.

Finally, the coroner is a typically Anglo-Saxon role, although our background of American and British fiction may lead us to think that it exists everywhere. It is a legal officer who in the event of suspicious deaths has the task of establishing the circumstances of death and the identity of the victim. The coroner may be a lawyer or a doctor, so sometimes he/she is a medical examiner, but often he/she is not. This also depends on the laws of each country or even, in the case of federal countries (like the United States of America), each state/region.

And then there’s the distinction between criminologist and criminalist. The two terms have different meanings in different countries.

In English, the criminologist is often defined as an expert in forensic science, so it can be a crime scene investigator and/or a forensic technician. The term “criminalist” can be understood either as expert in forensic science and as a synonym for criminal defence lawyer and criminal psychologist or psychiatrist. The choice of either term varies according to the different language variant (American, British, Canadian, Australian, New Zealand, etc ...) and common usage. Between the two, the term “criminologist” often prevails, because it is the one used in fiction. The British often avoid the term “criminologist”, which is more American, and use the specific ones, i.e. “crime scene investigator” and “forensic technician” or “forensic scientist”.

What about Italy? Here the use is different. The person who analyses the physical evidence is always defined criminalist (criminalista in Italian).

The criminologist (criminologo in Italian), instead, is an expert in criminology, i.e. the science that studies crimes, perpetrators, victims, types of criminal behaviour, prevention of crimes and reintegration of offenders into society, after serving their sentences. In short, it is an interdisciplinary field that combines expertise in criminal law, psychology, biology, sociology, and many other disciplines, and that focuses on the “who”, not on “where” or “how”, so the criminologist doesn’t participate in the investigation or trials.

Who, like me, writes novels that deal with forensic science has to consider the target readers, of which I myself belong, both concerning the terminological knowledge and from a geographical point of view. To avoid confusion in the reader, in the books of the Detective Eric Shaw Trilogy I tried to use simple terms, which are understandable and commonly used. For this reason I mention a “medical examiner” and not any specialisation of Dr. Dawson or his assistant, Dr.  Collins (who appears in “Syndrome” for the first time). I use the term “coroner” only once in a scene from “The Mentor” to indicate the presence of this figure or its representative at a crime scene, including a corpse. Actually, I mention the coroner’s van, without specifying who the coroner is.

Moreover, since I had to indicate the role of the characters who work for Scotland Yard forensic department (Metropolitan Police Forensic Science Service) with a single term and widely used in fiction, I chose the generic “criminologist” (if the story were set in Italy, it would be wrong ) instead of “crime scene investigator” or “forensic scientist”, which sound too technical or just bulky in a novel to indicate the person who is speaking, although they are the more correct in a British context.

Finally, to do honour to the habit of TV series, movies, and other novels by using the characters at all stages of the investigation, my criminologists go to the crime scene, do the analysis in the laboratory, but they all are also police officers (which is not always true in the UK), not only the detective chief inspector who heads the team (Eric Shaw), therefore they interrogate people, participate in the chases and arrest the criminals, and unlike the majority of real British police officers they usually have a gun.

When criminologists are wrong

Fingerprints are unique and for this reason are considered the most effective method to establish the identity of a person together with the analysis of DNA, which is much more difficult to find at the crime scene. But, unlike DNA which is compared by means of an instrumental procedure giving a response on which, except in case of manipulations of the sample, there are no doubts (even if it only provides a statistic), the examination of fingerprints is instead performed visually by a person. The computer can select some possible profiles that display similarities with the fingerprint found at the scene, but then the criminologist is the one carrying out a visual comparison and making a decision.

We know that the human factor always has a margin of error, yet we have realised that this can be true even in the context of the comparison of fingerprints only when some sensational cases of miscarriages of justice occurred.

One of the most famous concerns the terrorist attack in Madrid in 2004. A plastic bag containing detonators was found at the scene. A latent fingerprint was detected on it, which was then digitised and transmitted to Interpol. The automated comparison with the database of the latter had provided twenty results. Among them there was one that, according to an FBI fingerprint expert, presented a very high match, so much to bring them to say they had found the owner of the fingerprint detected at the scene. This conclusion was later confirmed by two more experts, both from FBI.

The fingerprint was of a Canadian, called Brandon Mayfield, a Muslim lawyer, married to an Egyptian woman. The man denied having anything to do with the attack, but was still arrested according to the discovery of his fingerprint.

Some time later another independent expert confirmed for the fourth time the conclusion of FBI, but shortly after the Spanish police claimed they had found the real culprit, the owner of that fingerprint (an Algerian, who was later incriminated for the bombing). Because of this, Mayfield, who really had nothing to do with the case, was released.

The question that arises is: how is it that four experts were convinced that the fingerprint found at the scene was his? After considering this, how much can you trust the use of fingerprints to establish the guilt of anyone?

And this case is not even the only one, although it is the most impressive.

Another one, for example, occurred in the UK, where a fingerprint was found at the scene of a murder (the victim’s name was Marion Ross) and was then assigned to a detective (Shirley McKie) who actually worked on the case. You might think about a typical example of unintentional contamination of the scene by the police, but the detective had never entered the bathroom where the fingerprint was detected and, since she continued to affirm that, she was accused of perjury and lost her job.

Then they realised that the fingerprint wasn’t hers. There had been, in fact, a human error by the criminologist who had performed the comparison. The detective regained her job, but at the same time as the real culprit of the murder had been found (his name was David Asbury) again thanks to a fingerprint, the court did not accept the latter as evidence, and he was released.

Again, in this case a mistake was made, with the aggravating circumstance that it’d had a further negative consequence: that of making the real culprit be released.

How many more errors like these are made and never revealed? How many people have been exonerated or, worse, incriminated and maybe imprisoned because of these mistakes?

We don’t know, but certainly all this highlights how the use of fingerprints or other physical evidence, whose identification depends largely or exclusively on a decision taken by a human, might not give certainties at all.

Of course, you can reduce the margin of error with appropriate precautions.

In Mayfield’s case the error was probably due to the fact that all experts involved knew that the man was a Muslim (which can cause a prejudice) and with McKie the fact that she worked the case (other prejudice), but also that those repeating the comparison after the first one were aware of the previous conclusion of their colleagues (comparisons should be blind).

All this concerns reality, which once again looks much more grudging of certainty than fiction.

I honestly cannot remember a single film, novel, or TV series in which the criminologist on duty made a mistake with the identification of a fingerprint’s owner. In fiction these professionals are shown as infallible, and if there is a mistake, it is due to a manipulation of the scene by the offender or is voluntary.

The latter cases include the story of Dexter Morgan, main character of the TV series titled “Dexter” (and the books by Jeff Lindsay from which the former is developed), the forensic haematologist who often alters his conclusions or manipulates evidence during investigations to cover his own actions as a serial killer, or to ensure that a certain person isn’t arrested so that he could kill them.

In short, fiction tends to enhance the cunning of the protagonists, and defects, when they exist, never concern their job. Typically, the investigator drinks (or even uses drugs), eats little, sleeps little or nothing, and maybe doesn’t even wash himself, but when it comes to investigate a murder he is always very clear-headed!

An example of this cliché is the series of books by Michael Connelly starring Detective Harry Bosch, from which in recent years the TV series “Bosch” has been produced by Amazon Studios.

In the second book, “Black Ice”, there is a mistake in the identification of a fingerprint’s owner, but it is something voluntary and orchestrated to distract the investigations and not a simple mistake made by those who made the comparison.

Human error without an ulterior motive doesn’t work so much in fiction, perhaps because it is too realistic.

I must admit that while writing the Detective Eric Shaw Trilogy, I haven’t used and don’t intend to use such errors by the main characters. Sometimes they may miss a detail (because this is useful to the plot), but never fail a comparison of a fingerprint. The errors at best are made by the antagonist.

This doesn’t mean that I don’t exploit the human factor. Detective Shaw, in fact, uses this type of vulnerability in forensic science to domesticate evidence, as it happens in the case of Johnson in “The Mentor”, in which Shaw causes that the man’s fingerprints are detected on the murder weapon to induce him to confess.

But what if, following his own instincts, he would aim to the wrong person? Let’s consider that he is absolutely sure that he had found the culprit and forces the situation by manipulating evidence so that this person cannot escape justice.

What if, some time later, maybe years later, something would turn up that casts doubt on the validity of that belief?

This is the possible doubt that I will explore in the final book in the series, “Beyond the Limit”.

DNA and fingerprints don’t lie

One of the phrases that you hear most often in TV series that deal with forensic science is that evidence, unlike people, doesn’t lie. A variation of this statement is that the dead (their bodies), unlike the living, don’t lie. The gist of it is always the same: physical evidence includes the answer to find the author of a crime (Mac Taylor from “CSI: NY” seems to have so many of them available in the photo), you just have to find them and interpret them correctly.

In reality, however, most of the physical evidence that is found at the scene of a crime doesn’t allow to uniquely identify a person, is subject to the problem of contamination, and therefore can at most serve as supporting evidence to prosecution, but isn’t sufficient to send someone to jail.

The identification of a person (who is guilty or otherwise involved in a crime) can be successfully accomplished, in the absence of witnesses (which, however, can lie!), only if it involves some items found on the scene that belong exclusively to that person, actually, that are part of that person.

These are the biometric identifiers. There are two categories of them. The first includes physiological characteristics, such as fingerprints, DNA, facial, iris, or retina recognition. The second relates to behavioural characteristics, such as gait, voice, or handwriting.

These identifiers are typical of a specific person, but some of them are even unique and stable throughout life, and may be left at the scene of a crime.

I’m obviously talking about fingerprints and DNA.

In reality, finding this type of physical evidence that can be used to identify the culprit is quite difficult. Fingerprints, in particular, are everywhere at a crime scene and are often so incomplete and numerous that they cannot be used, unless they are found on the murder weapon. DNA is even rarer to spot. For both of them you must still do a comparison to determine their origin (for example, taking a sample of cells from the mouth of a suspect, like Greg Sanders from “CSI” is doing in the photo, next to a character played by Justin Bieber), but there are also databases (however, a still limited number of countries has a DNA database), therefore from a fingerprint or a blood trace found on the scene of a crime you can, at least in theory, trace back to a person, although this person has not yet been connected to the case.

This is a rare case where fiction resembles reality.

Even in fiction it’s unlikely that the culprit leaves behind fingerprints and DNA that can be used, but the reason is that, if they did, the case would be solved too quickly and there would be no story to tell!

This doesn’t mean that this kind of evidence doesn’t appear in TV series, films, and books. Far from it.

In fiction, fingerprints and DNA are almost always found during the investigation, but they belong to someone who is not directly guilty, which, possibly, tends to send off-road criminologists and investigators and to distract the reader/viewer.

But once again fiction highlights the absolute value of this type of evidence (well, it does so even with fibres and paint!), without considering some issues that affect them.

For example, while watching a typical episode of “CSI” you will have the impression that if you enter a fingerprint found on the scene in the computer you just need a short time to get a single finding: the one of the fingerprint’s owner.

It isn’t so at all. Apart from the fact that the time isn’t short at all but depends on the size of the database, you should also consider that the computer could deliver much more than one probable finding and none of them will be a 100% match. This is the moment when the expert intervenes and makes a visual comparison between the footprint available and the one in the database, to determine if they actually match and perhaps exclude some results, if not all. It’s a human being the one who makes this decision and, as such, may make mistakes.

Yet both in fiction and in reality (in this regard I will present some outrageous mistakes in the next article of this series) the fingerprint is considered an overwhelming proof, since there aren’t two people in the world with the same, identical fingerprints.

DNA is even more overwhelming. Here too it depends on its uniqueness (except for monozygotic twins), but not everyone knows that the DNA analysis doesn’t give an absolute result. In this case, the human factor isn’t involved, because the analysis speaks for itself, but its results are statistical in nature, since obviously you don’t analyse the whole available gene pool, but only a certain number of loci. It is likewise true that the probability that samples of two different people (not twins) returns the same profile is as low as to be considered zero.

So yes, DNA is a proof that doesn’t leave room for doubt, whether it is reality or fiction, except that in the latter its detection and its analysis is simplified, and they often take place in a ridiculously short time.

At the end, the criminologist is all smiles with a sheet (or a tablet) in his hands and goes to his boss to show them the result, after making the analysis and the comparison to the database within a half-hour. But then you have to hurry, because the case should be closed within the day and this proof will be only one of the many which will make the characters come closer to the solution, though without being the solution itself.

Even in the Detective Eric Shaw Trilogy, I used fingerprints and DNA. In “The Mentor” I talk about a case of tampering of fingerprints, which the protagonist uses to push a suspect to confess. In “Syndrome”, however, the fingerprints on a murder weapon will be an important element in the identification of the culprit. I cannot go into details, you must read the book to learn more (it isn’t available yet in English, sorry!), but I can say that I explained how the fingerprints were collected and that there are different ways to do that according to when they were created.

The first, which is also the most common one in fiction, is when you brush a dark powder on a surface to reveal any latent fingerprints (like in the photo above with Eric Delko from “CSI: Miami”).

In reality (and also in my books) this powder is called silver-grey and is actually used for this purpose to highlight the papillary lines, those that have been imprinted on smooth surfaces mostly due to the presence of sebaceous material on the fingertips (in “Syndrome” I took yet another small licence, indicating a surface on which it is generally not easy to detect fingerprints, but I was deliberately vague, suggesting that it was really smooth or assuming that criminologists, as usual, were lucky). This method is used only if the prints are relatively recent, but, if they date back to more than two or three days, they may have dried up, so it is necessary to use a chemical called ninhydrin, which reacts with the amino acids present in the sweat, generating a visible colouring.

Also, DNA makes its appearance in my series (on blood stains in “Syndrome”) and again, in the best tradition of fiction, it is used mostly for reshuffling the cards and complicating the job of the protagonists.

But, if nothing else, I can say I gave a touch of realism by showing that they had to wait at least a few days before getting the result of its analysis.

The fibre that nailed the murderer

There is nothing like that. I am referring to the title of this article. Despite what happens in fiction, where often the resolution of a case depends on the discovery of a fibre, typically a single and isolated one, found at the scene and on the victim (it often happens to Sara Sidle from “CSI”; see photo), in reality such a fibre would serve to demonstrate just nothing at all.

It’s clear that certain materials release tiny fibres, which, if desired, can be compared, for example, with the clothes of a suspect or with some other textile object that belongs to the latter.

Let’s completely leave out the usual imaginary databases, like the one, in one of the latest episodes of “Bones” I recently watched, that linked a synthetic fibre to the mat of a luxurious car, which, as usual, was a limited series, allowing for confirmation of the suspect. However, even assuming that the database exists (I don’t believe so), I have strong doubts that a particular fibre is only used for the mat of a car model (we know they do them all in China, often in the same factory from which those for the cheapest small cars come).

Instead, let’s get back to the case where there’s already a suspect, and you can make a comparison. But even if this comparison is positive, what would it demonstrate? Nothing.

Identical fibres are found in very different materials, moreover our fibre could be there because of an innocent contamination preceding the murder or because it was transferred to the victim after a previous contact with someone totally unconnected with the facts.

For this reason, fibres are only supporting evidence that therefore doesn’t add certainty.

This applies also for hair. In this case, a comparison may be more useful, as it helps to narrow the field. If a long blond hair is wrapped on the murder weapon, for instance, and the suspect has long blond hair of the same colour and similar characteristics (such as size or the fact that the colour is or isn’t natural), there is a certain probability that it belongs to that person, but probability is not certainty and this makes it just supporting evidence.

The real breakthrough would be achieved if the hair in question still had the hair bulb, from where you can collect and then analyse DNA. If there weren’t a good reason, independent of the murder, able to explain the presence of the hair on the weapon, the suspect would be in big trouble.

Another kind of evidence that can be found at the scene is a shoe print, maybe a bloody one. If it’s different from that of the victim, almost certainly that shoe print belongs to the killer or other person who was with him at the time of the murder.

The shoe print can allow criminologists to trace back to the shoe size and, if it shows a particular design, even the brand (especially if that famous database of shoe soles existed!). Once again, it can be very useful for a comparison. The problem remains that, if it isn’t from unique handmade shoes (quite rare nowadays), this type of evidence does not give certainty, unless you find a specific correspondence concerning the wear of the sole, due to the unique way that each of us has to walk and wear out some of its areas. In this case, the time factor becomes crucial, because the wear and tear continue, if the murderer keeps on wearing those shoes. You have to make the comparison within days, at most a few weeks, otherwise you won’t find any matches.

Like shoe prints, there are other types of characteristic signs. Let’s consider a screwdriver used to force a window. It certainly leaves a mark on the frame, which corresponds to its shape. If the screwdriver isn’t new, it’s become worn, then the mark it leaves behind is unique. As for the shoes, and for the same reason, the comparison, however, must be done in the shortest time possible.

What if the screwdriver was the murder weapon?

Certainly it left a mark on the body of the victim, maybe not as distinguishable as on the frame, unless it has affected a bone. Finding a similar weapon at the suspect’s house and detecting traces of blood on it (which, as we all know, is very difficult to remove, so much to stay there even if you don’t see it with your naked eye) could be an overwhelming proof. Even more if there are his fingerprints on it and he doesn’t have an alibi for the time of the crime. Unless someone has decided to frame him, using his screwdriver, which happens more often in fiction than in reality.

To discover the murder weapon, we have often seen criminologists in the TV series get to pierce gelatine men or carcasses of animals with objects found in the house of the suspect. Usually, this wasteful practice leads nowhere, except the rare case that the suspect was framed.

The real culprit, of course, gets rid of the crime weapon!

Even more expensive is the practice of raging on surrogates with random objects that the protagonists of CSI simply place on a table and try one by one. The aim is at least to understand which weapon they must look for. The possibility of catching the right one among an almost infinite number of objects that tear the meat in a similar manner is close to zero. Well, in this case, instead, immediately a strange tool comes up (what luck!) that perfectly corresponds to the shape of the wound. Usually, when it happens, it provides valuable information, since a suspect uses something like this for work or hobbies.

And then there are the famous traumas from a blunt object.

The victim was hit in the head by an object that might be a hammer, a mace, a lamp, a trophy or something. The impact caused a peri-mortem trauma (sometimes not immediately visible, but it appears in the form of haematoma after the body is kept in the freezer for a few hours) and maybe left an evident mark on the skull bones.

And so the criminologists, with great fun, put on their overalls and goggles (that outfit that they do not use at the crime scene; see photo from “CSI: NY”) and begin to hit the poor dummies, until they find the right object.

The mechanism is identical to the case of the screwdriver: if the weapon is found at the suspect’s home, someone has framed him; if it isn’t found, however, they will be able to locate it by taking chances among thousands of possibilities, shamelessly wasting puppets, gelatine and pig carcasses, and from there they’ll unveil the unthinkable culprit that uses the same type of tool to make some innocent do-it-yourself. Then, by analysing his toolbox, they will find a bar with the same profile, which will be bloody or recently cleaned with bleach (unlike other tools that are filthy).

I could go on like this forever telling you about all these proofs that are the daily bread of criminologists in fiction and whose discovery is, consequently, the basis of the plots of crime stories focused on forensic science.

As an author, I use several of them as well, especially since I know that’s what the reader would expect. And then, let’s face it, it’s fun to use them! But I prefer to highlight how their usefulness is limited, often exploiting them as elements that support the investigation process made of intuition and imagination, or that exclude certain scenarios. This is because this evidence is often most useful to exclude than to confirm.

For instance, in “Syndrome”, an interesting element when analysing the scene of two murders is the total absence of shoe prints in a nearly immaculate flat, where a dirty corpse lies whose soles have some soil. This finding brings Detective Shaw and his team to conclude that the murderer has deleted these prints or, even better, that the victim has never walked on that floor, where he was just dumped, therefore that isn’t the primary scene of the crime.

In “The Mentor”, instead, I exploit the case of a haematoma that appears later (because it isn’t visible on the corpse immediately after death) and reveals that the victim was pushed with a shoe whose pointed profile reminds the footwear of a woman. This leads investigators to speculate that a woman is the killer (or the killer’s accomplice) and pushes Detective Leroux to question an eyewitness, who maybe saw someone leaving the crime scene.

The beauty of it is that I didn’t learn much of this by reading treatises on forensic science, but reading the novels by Patricia Cornwell, watching “CSI”, “Bones”, “NCIS”, “Body of Proof” and many others. All of which, taking a cue from science to create stories, in addition to entertain people (as they are entertainment tools), somehow enrich the latter, leaving them with a little more knowledge and, at the same time, with a certain curiosity to learn more.

Lucky criminologists and maladroit criminals

One of the most common ways to find out the culprit of a crime, in fiction, is to let a tiny physical evidence be found on them, or maybe their car, thus linking them undoubtedly to the scene or even the victim; or to find (always unique and very small) evidence on the scene or the victim that is certainty linked to a suspect.

It seems easy to detect such evidence (Abby Sciuto from “NCIS”, in the photo, does it all the time) and, when it happens, this discovery is almost overwhelming, often pushing the suspect to confess.

A typical example is some paint found on a car forced off the road by another vehicle. It is quite common that, following a violent impact, some paint is transferred from one car to another; indeed, it almost always happens. Think about all the times you found a little gift on the bumper of your car by someone who leaned to it while parking or who made a mistake while exiting from a parking space.

But is it really possible to trace back the model and manufacturing year of the car? Generally not, because the same widespread paints are used in different models, often different brands, in different periods, and even if the type of paint is determined (besides the colour, I mean), this doesn’t narrow too much the search field. The only exception occurs when you have to do with some very rare paint used in an equally rare vehicle, for example, a limited series or a classic car with the original paint. Usually here a sci-fi database comes out like magic, which in five minutes at most starting from a paint chip pulls out the photo of the car that, incidentally, is so rare that very few people in the whole town (and we often talk about big towns or even cities, like New York) have one, including a potential suspect that shows another small link with the victim.

There you have it: a tenuous link with the victim plus the same paint of their car, and the suspect collapses.

“Yes, I killed her!”

Sometimes I wonder why these criminals are so maladroit or unfortunate enough to use rare vehicles to carry out their misdeeds.

This so unusual that (almost) never occurs in the real world. Usually, even being able to go back to the colour and perhaps the brand of the car is just one more element to substantiate the suspicions about a specific person, but doesn’t add any certainty.

But there is a particular situation where the paint can be important and become an irrefutable proof: when a car has been repainted several times and the same stratification is found as physical evidence.

But a doubt always remains. Are we sure that the transfer took place precisely during the crime and not earlier? Most times we are not.

This is the problem that plagues all kinds of residues, whether it’s paint, glass, dirt, and even the one coming from a gunshot: we cannot establish the precise moment when it settled.

Let’s think about glass. The murderer broke a window to enter the house of the victim. The suspect has a tiny fragment of glass on them. Is it the culprit? Assuming also that the glass is of the same type, it could also be someone who has been on the scene after the crime, or maybe who visited a neighbour of the victim, in the same building, who has an identical glass, which is broken.

Here, as for the paint, applies the case of very rare types of material, but that would be a stroke of luck.

What about the soil? Well, in TV series such as “CSI” it isn’t unusual that from micro-grains of soil found under the soles or on the clothing of a victim they come to find out exactly the primary scene of the crime. There is always some pollen from an exotic plant that is grown only in one place within hundreds or thousands of kilometres, where, despite a size of several hectares, our investigators discover more physical evidence pointing to the culprit. Obviously, there is a special database with all pollens: you just have to do a banal search by image. Never once it happens that they find a very common soil or that the place of origin is so broad to be a dead end, or that it is then found out that the soil ended up on the victim as a result of a chain of common contamination that leads to absolutely no result.

And then there are gunshot residues.

When firing, a cloud of residues is ejected by the weapon, containing elements such as antimony, barium, and lead, with a composition that is typically specific of a certain weapon with a certain type of bullets.

If a person was killed with a certain weapon, which was found, and the same gunpowder residue produced by it is detected on the hand of the suspect, it is very likely that he/she pulled the trigger.

What if they have used a pair of gloves? Well, residues may still have ended up on their clothes, only that in this case there would be no certainty that they shot. The suspect may also have been in the vicinity, while someone else was shooting, or even got into contact with the murderer at a later time and have nothing to do with the crime. On second thought, if they shook hands with the murderer shortly after the shot, they could have the same gunpowder residue, even if they aren’t the culprit. It gets even more complicated, if we’re dealing with people who use weapons and are routinely subjected to multiple contaminants from gunshot residues.

In short, all the physical evidence that is used very often in fiction (and we love it) to nail the culprit, in reality, most of the time are totally or nearly useless.

But in fiction we like to have fun and authors of crime fiction like me are in their element when using this. For example, I mentioned gunshot residue in the second chapter of “The Mentor”, in which Detective Shaw leads a man suspected of being a killer for hire to confess a murder, after having framed him with false fingerprints on the murder weapon. The suspect, a certain Damien Johnson, is led to think that he cannot prove his innocence (there is also the fact that he isn’t innocent), because, although during the crime he was wearing gloves and so couldn’t possibly leave fingerprints, he has recently used a weapon during his job as security guard and then the gunpowder residue along with the false evidence nails him. To refute it he should say that he used a pair of gloves, but that would still be a confession. Eric knows that the two residues may not match, but Johnson, who is aware to be guilty, is so resented about being framed that he doesn’t even think about it (perhaps he even doesn’t know that the residues may have different compositions: indeed he isn’t a criminologist!) and he decides to negotiate a plea bargain. The story then quickly goes on, the character is put aside, and the reader doesn’t think about it any more.

Similarly, no one is scandalised if in “Bones”, when they examine the skeleton of a victim (who knows why, anyway, they always decide to strip the flesh from the victims to find out how they died, even from all those that are found whole, while in other series a normal autopsy is more than enough), they always find only a tiny trace embedded in a bone (of course) from which a series of clues comes out leading to the killer. If we were to reflect on each decision made by the characters, we would soon realise that they could have made many different ones, which would take them completely off the track. What else could I say? They must be geniuses (and Temperance Brennan constantly emphasises that), but on second thought, it seems that they are just very lucky!

Could it be the reason why, in fiction, the cases are solved in a day, but often in the real world after years of investigation, even when they seem to be solved, you are never sure you have found the real culprit?

Yes, even in this case we cannot deny it: although reality often exceeds imagination, fiction is much more fun and, above all, reassuring.

Crime scenes and artistic licences

Being a crime thriller fan myself, as a reader and author, but also viewer, I’ve always been intrigued by the way in which reality of investigative procedures, in particular concerning forensic science, is reinterpreted in fiction (including TV shows and films) for showing it in a way that is comprehensible and able to entertain the audience. One thing I have always noticed is that anyone who is the protagonist of the story, whether it’s a detective, a medical examiner, a criminologist, a prosecutor, a lawyer or even an anthropologist, that character automatically rises to a crucial role in the investigation.

Of course, the procedures vary from one country to another and with respect to the United States, a frequent scenario in which a reader/viewer comes across, even from state to state, so it is not absurd to think that depending on the location where the story takes place the dynamics between people who work to discover the culprit of some crime (generally a murder) are ruled differently.

But, beyond individual cases, I’m more inclined to think that this phenomenon is simply the result of artistic licence. Except when the protagonist is a detective, which by definition has the role to investigate, all the stories with different positions as protagonist must necessarily yield to the will of their creator, so that action involves the main character, and therefore the story works.

The role of medical examiner is one of the most popular. Do you remember “Quincy”? It is a series broadcasted by NBC between the 70s and 80s that features a pathologist who finds himself investigating cases of murder. I was too young back then, but I happened to watch it more recently on Sky, and despite the effect of the passing of time, I always find it very compelling.

A similar situation is seen in TV series such as “Crossing Jordan”, “Body of Proof” or the recent “Rosewood”, without forgetting the fiction series of Kay Scarpetta by Patricia Cornwell: all series in which pathologists or medical examiners (there is always a lot of confusion about the terminology, which gets worse because of the translations into other languages) will get busy to find the culprit, as if they were detectives, and often risk their lives.

The role of the criminologist, however, owes much to the CSI franchise, which has brought it to light for the first time, so that significant interest in it was created in the public and increased the number of young people who wish to pursue this career, and then maybe find that it is much less exciting and decisive in the resolution of a case than how it seems on TV! In this regard, I wrote about the “CSI effect” in an old article.

In the constant search for a possible new star of the investigations that it is not the classic detective, they even came to the forensic anthropologist in “Bones”, a TV series inspired by Kathy Reichs’s (who is a real forensic anthropologist) novels, where Dr. Temperance Brennan along with their colleagues at the Jeffersonian Institute (which does not exist!) in Washington solves brutal murder cases. Okay, along with her is also FBI Special Agent Seeley Booth, but, let’s face it, the engine of all is Brennan.

The reality on how you carry out the investigations of a murder is different, of course, but that doesn’t matter, because we’re talking about fiction, not documentaries. What matters is that the story works and that the reader/viewer is having fun.

And, anyway, the artistic licences go well beyond the roles of the characters. Just think of the clothing on a crime scene. Whoever has watched only an episode of “CSI: Miami” has certainly noticed criminologists wandering among corpses in elegant suits (men) or impeccable lady’s suit complete with shoes with high heels (women). And all this in hot Florida. Where are the protective overalls, shoe covers, hoods, and everything else? The maximum that you can see on them is latex gloves!

Not to mention the fact that at the appropriate time they all become perfect shooters or skilled negotiators or that the most insignificant physical evidence (e.g. the usual fibre) is enough to nail the murderer, since there is a database of everything.

In short, artistic licences are everywhere, and we are not always able to identify the boundary between reality and fiction. And, all in all, we aren’t even interested.

Personally, being a biologist, I am fascinated by forensic science, but rather at a theoretical level. Having worked in the past in a university laboratory (although my “investigations” were in the field of ecology, so definitely a lot more cheerful!) I know perfectly well that it is a job made of slow procedures, often not entirely reliable, full of repetitions and inconclusive results, where you produce a flood of data of which only a small part is really useful or usable. If the stories narrated what it really means to analyse all the evidence from the scene of a crime, their consumer would be bored to death.

This is why you come to the artistic licence: in books, movies or TV series, each event must push the action forward and it doesn’t matter how the characters are dressed, what their capabilities are or what exactly their roles should be.

So when I found myself writing for the first time a procedural crime thriller, “The Mentor”, on one hand I tried as much as possible to keep a certain inherent logic within the plot as well as a substantial scientific plausibility, on the other hand it was me as author who created the rules that govern the world in which my characters move.

This is how my version of the scientific department at Scotland Yard comes from, where criminologists are almost all also police officers (which is not true in reality) and, as such, not only they own a weapon (most British police officers are not armed), but use it with ease. In addition, I never specify if they are wearing any special protection on the scene, apart from the usual latex gloves, but then I don’t even say the opposite.

Even the explanation of their ranks within the police is minimized according to the needs of the plot. For example, the main character, Detective Shaw, is chief of a scientific team, but only in the second book I clarify that he is a detective chief inspector, because he mentions a possible promotion, which then will fall into the plot of the final book of the trilogy: “Beyond the Limit”. Similarly, in the second book, you discover that officer Mills became a sergeant: the reason is to further show the fact that two years have passed.

Sometimes, moreover, the characters can count on futuristic technologies invented by me (like the program used by Martin Stern in “Syndrome” to create an explorable computer recreation of the crime scene) that accompany the real ones, for which I performed specific research (the detection of fingerprints with silver/black powder or blood with luminol).

I also admit that only half of such research is derived from the study of techniques and procedures used in real life, through an online course that I attended (created by the University of Leicester) and of course Google, while the other half comes from my TV, cinema, and fiction background.

Besides, the reader uses it as a term of comparison and, basically, reproducing some aspects already seen in a book or on TV does nothing but reinforce the suspension of disbelief and, ultimately, increases the enjoyment of the novel.

The purpose is to entertain, and artistic licence is and always will be an essential element in achieving this goal, even when it comes to the most rigorous matters, like science.

CSI Effect: forensic science between reality and fiction

Starting from 2000, the first season of CSI: Crime Scene Investigation debuted on TV and soon became one of the most popular “procedural” (i.e. describing the police/investigation procedures) series in the world. Similar series, including its spin-offs (CSI:Miami and CSI:NY) but also the various NCIS, Bones, and so on, have followed in its footsteps almost always repeating the same success.

They have allowed to bring the public closer to a previously little known aspect of the investigation of crimes, even if within written fiction it had already begun to carve out an important position (for instance the novels in the series of Dr Kay Scarpetta written by Patricia Cornwell, although the perspective was slightly different), namely that of the meticulous forensics work based on physical evidence and analysis, as opposed to the classic investigation made mostly of intuition.

The success of these series has, however, given rise to a phenomenon that has still negative consequences in the field of the real forensic science, or rather of its application in the legal field. This phenomenon is called “CSI Effect”.

It is due to the fact that what these series show is mostly fiction, even if there is some reality. The viewer (or the reader in the case of the novels), who isn’t an expert in the field, is often unable to distinguish fiction from reality and that generates expectations regarding the work of real forensic investigators, in relation to actual crimes, that are anything but realistic.

In the various CSI series and the like, for example, we see that all cases are solved thanks to the discovery of physical evidence that is irrefutable to link a suspect to the crime scene and then identify them as the culprit.

Beside the fact that in reality the physical proofs that can be used are often very few and difficult to interpret, it is rarely highlighted that just a few of them are to be considered really relevant from a legal point of view. This category includes those that can be 100% (or almost) traced back to a single person. In other words, the only irrefutable physical evidence is a DNA match (which has an error rate practically equal to zero, unless you have to do with identical twins) and the dear old fingerprints. But even the latter have led to sensational errors, since the identification may present a not entirely negligible percentage of uncertainty.

Then you must consider that finding identifiable fingerprints is not nearly as common as it seems, while in almost all cases there isn’t the slightest trace of DNA.

All other physical evidence often proves absolutely nothing. When in the TV series we see criminologists get to a suspect by a small fibre, with the support of a mysterious (and even a little science fiction-like) database, and how this leads to their arrest and presumably to their conviction, well, in those cases fiction prevails.

This physical evidence in reality can be traced to a certain person with very low likelihood, because there are a number of factors why for example the fibre I mentioned before can come from many different objects and especially can be transmitted entirely by accident, through a chain of individuals, to the crime scene.

In a nutshell, in the real world it may easily happen that, in a case where there is a lot of non-relevant physical evidence (so no fingerprints and no DNA), this is by no means sufficient to convict someone. On the contrary, it may happen that there is a sentence based on a whole series of proofs that do not include any physical evidence.

Yet people watching these TV series has the false perception that this cannot, and indeed should, never happen.

This false perception, which is actually called “CSI Effect”, is the source of so many conflicting opinions from the media and the public about famous crimes, but also poses a big risk in situations where it arises in those who have the task of judging in the context of these crimes and are at the same time common people. I’m talking about jurors.

Jurors are people who do not always have the scientific background to really understand forensic science or the probability related to it, and this fact has led in some cases to judicial errors. In fact, it has happened that innocents were convicted because jurors had given too much importance to physical evidence with a low relevance, just as the classical fibre on the body of the victim who had vaguely to do with the suspect. In others the opposite happened: a culprit was acquitted because there was no physical evidence that gave the “certainty” of their involvement, although there were a thousand other facts or clues that gave rise to very few doubts (like motive, opportunity, and even eyewitnesses).

I heard for the first time of the “CSI Effect”, which is being studied since 2006, during an online course in criminology from the University of Leicester that I attended at the beginning of 2014, and I realised that I’m not free from it either.

I am a huge fan of these TV series (and also of Cornwell’s novels) and, even if I am fully aware that at least 60% of what I see (or read) is totally unreal (can you recall the typical DNA identification made in five minutes?), I was often pushed to think that the work of the forensic squad was really central, indeed indispensable in solving a crime (especially in murders).

This thought is so rooted in ordinary people who love mysteries and thrillers that they expect to see it in movies, TV series, and novels.

And we, thriller authors, end up giving them what they want, because what we write is not and should not be reality, but is fiction. You must not forget that.

Some of us try to be as realistic as possible and others, instead, move considerably away from what happens in the real world, but virtually all the authors of these genres bend reality to the needs of the story, so that the latter works and, in the meantime, the suspension of disbelief is maintained, which often has nothing to do with reality but only with its perception. Because, let’s face it, reality rarely fits the times and ways of narrating stories, or otherwise it can sometimes become boring for the reader who has specific expectations within a genre. Even when we write true stories, we end up novelising them so that they work.

I admit I did too with “The Mentor”, indeed I did it in a very strong way.

In the end, the only reality in it is London and its streets (some details of which are completely accurate, because I visited almost all of those streets in person) and some very general information about the organisation of the police (like the separation between the Metropolitan Police and the City of London Police). Concerning the rest, I took full licence.

In addition to assume that the employees of the forensic department at Scotland Yard are policemen (in the UK there is often a significant separation between the police, the investigators who work on the crime scenes, and the technicians who analyse the findings) and show a continuous and direct cooperation between them and a Murder Investigation Team, or making them use guns with too much ease - all essential devices to tell the story the way I wanted to (in this regard I wrote a note at the beginning of the book ) -, in my novel you can find clear traces of the “CSI Effect”.

On one occasion, for example, the main character, Detective Eric Shaw, manages to nail the culprit with anything but crystal clear physical evidence. In another, on the contrary, a myriad of clues together with the absence of a solid alibi does not seem sufficient to hold a suspect in custody even for a minute longer, because there is no physical evidence.

All this was done in order to bring the story in a certain direction that in the real world would never have occurred. But, remember, we’re always talking about fiction , so not only I could, indeed I had to do that. The important thing is to be consistent when you do it.

Here I enjoyed making both situations quite plausible, with explanations that are in line with the suspension of disbelief, so that, although these are a bit of a stretch, so far no one has perceived them as such (at least nobody told me they had), partly because of the way I presented them, but mainly because any reader of thrillers and mysteries is a victim of the “CSI Effect”, too.

And, although they are aware of it, after all, they like to think that justice is made of white and black, of incontestable evidence without which you don’t go to jail, that it is more likely that the culprit is caught rather than an innocent pay for a crime they didn’t commit. All this is reassuring against a real world made of incomprehensible statistics, uncertainties about the guilt, miscarriages of justice, approximate investigations and more, that we don’t like and that certainly don’t entertain us as, instead, fiction does. “Crime fiction” in all its facets is and should be entertainment. Let’s leave reality to documentaries and non-fiction.