Forensic science and police procedure – how the investigative process really works

(Article originally written for the Guppy Chapter of Sisters in Crime.)

The CSI effect. We’ve all heard the term, but perhaps only those who work in and around law enforcement and the judicial system wince with pain each time it enters their field of view. The term was coined to describe the way the TV show CSI: Crime Scene Investigation (and its various derivatives) has warped the popular perception of how forensics, crime scene investigation, and the investigative process in general, works. This warping effect has embedded itself to such an extent that some judges feel obliged to warn juries in advance that they must disregard whatever they might have gleaned from such shows when they sit at trial.

So what is myth and what is real when it comes to modern crime investigation?

Picture attribution: World Skills UK CC 2.0

First, an introduction: why am I qualified to talk to you about this?

Well, firstly, I’ve been writing for a long time. 23 years and 7 novels unpublished before becoming an ‘overnight’ success. I was born in England, but spent a decade working in India and, as a consequence, write two award-winning crime series set there. My debut, The Unexpected Inheritance of Inspector Chopra, was a bestseller, a Sunday Times 40 best crime novels published 2015-2020 pick, and translated into 16 languages. The series won a Shamus Award in the States. In 2021, Midnight at Malabar House, the first in my Malabar House novels set in 1950s Bombay, won the Crime Writers Association Historical Dagger, the world’s premier prize for historical crime fiction.

More importantly, for the past 16 years I’ve worked at University College London’s Department of Security and Crime Science. I’m not an academic but help manage some of our larger projects and research centres, working closely with researchers examining an array of crime types: trafficking, cybercrime, terrorism, etc. We work with police forces and law enforcement agencies around the world. For instance, one of the centres I help run is the Dawes Centre for Future Crime. I bet you’re now picturing Steven Spielberg’s Minority Report! To be clear, in that particular film, science was conspicuous by its absence – future homicides were predicted by three ‘psychics’, known as pre-cogs, who would send Tom Cruise racing around to stop the would-be murderer in his or her tracks. In the real world, academics tend to focus more on using data and scientific research rather than complicated stunts.

Myth  #1 – The criminal mastermind!

One of the key insights of crime science is that “even good people can do bad things, given the right opportunity”. This helps to explain why people with no prior history of transgression can commit the worst crimes. A simple example is someone becoming drunk in a bar, engaging in an argument, finding a glass or other weapon to hand, and violently attacking another person. Or a stockbroker committing insider trading fraud simply because the opportunity arises to do so.

The truth is that most criminals are opportunistic, rather than having some sort of ‘genetic disposition’ towards crime. Most are also ‘intellectually challenged’ i.e. stupid. The suave, refined, Hannibal Lecter trope is hugely misleading. As is the idea that the fastest growing and most ubiquitous form of crime today – cybercrime – is carried out by nerdy teenagers in hipster T-shirts sitting in their mothers’ basements.

Cybercrime is now the preserve of organised criminal gangs. From ID theft to phishing scams to cryptocurrency fraud to cyberwarfare, OC gangs have the finance and muscle to recruit those with the skills to carry out such crimes and to do so in a coordinated manner. Most law enforcement agencies are vastly outgunned – they lack the skills, the funding, and the person-power to compete. Things are changing, however, as lawmakers are finally cottoning on to the scale of the problem and throwing money at initiatives and centres to get a handle on things. But for years it’s been like getting the Titanic to change course.

Myth  #2 – Forensic science moves quickly

In CSI and other shows, the ever-so-cool detective/forensic scientist/all-round action hero finds a hair or a partial fingerprint and within hours it’s been whizzed through the ‘system’ and, hey presto, out pops a tangible lead, and/or a list of associated suspects/known associates, conveniently with a set of up-to-date addresses, for a swift SWAT takedown. Yeah… Um. No.

In reality, if a case is not high profile or political – and 99.99% of them are not – then the level of forensic science resource allocated to the scene may be insufficient to collect all available evidence. Next, a whole heap of admin and paperwork has to be completed as part of both the chain of evidence (very necessary!) and the process of requesting forensic analysis. That analysis – usually outsourced to a hired lab – can then take weeks, if not months. For instance, the DNA case backlog is enormous in most western countries. This is one reason why sometimes suspects unable to achieve bail are kept under arrest for inordinate lengths of time before their case can make it to trial. I stress that this isn’t the fault of law enforcement or forensic scientists – there’s simply too much incoming for the number of skilled people available.

Myth #3 – Justice always comes through in the end

Afraid not. Miscarriages of justice are commonplace. But this isn’t necessarily because of police or judicial incompetence. It can often be because of bias in the interpretation of forensic evidence, a topic we don’t often hear about, particularly as it doesn’t make for racy action sequences on CSI-style shows. Such shows have trained us to believe that forensic evidence is the gold standard. It’s science, and science doesn’t make mistakes, right?

In a sense, yes, science, when done correctly, should be exact. But the problem is that forensic evidence can be subject to ‘interpretation bias’ or error. Different forensic experts can interpret the same evidence in different ways, given a particular set of circumstances, or depending on whether they are being engaged by the defence or prosecution. This dynamic is constantly on display in jury trials.

These days even DNA evidence can be challenged; for instance, by accusations of forensic evidence transfer – the idea that evidence has been transferred accidentally from the crime scene to a suspect. Recent research has shown that this is a lot easier to do than was previously imagined. Trace evidence hangs around for a lot longer than was once thought possible.

So what really happens?

One of the most common anxieties among crime writers concerns the accuracy of the investigative process. The good news is that readers, by and large, are less worried about the accuracy of every aspect of the investigative process than they are about plot and characters. If you keep the pages turning, and don’t make obvious errors, they will go along with you for the ride. In fact, in some cases, you will have to abandon reality in order to avoid bogging things down, for instance, in the depiction of the time it takes to process lab results. This isn’t a licence to be lazy. It’s still important to make every effort possible to portray an investigation as correctly as you can.

What is an investigation?

The manner of investigation that takes place clearly depends on the type of crime novel. A police investigation will differ considerably from the investigation an intrepid journalist undertakes. A private investigator will have freedom to pursue actions that a police detective would consider beyond their legal remit. A legal thriller will showcase an investigation involving paid investigators, police, and revelations in court, some of them from specialist experts. Nevertheless, there are certain investigative elements that tend to pop up in most crime novels, to a greater or lesser degree.

Analysis of the crime scene

Certain things have to happen at a crime scene. These apply particularly to police procedurals and contemporary crime fiction, but the results from these activities also pop up in most other kinds of crime genre. So, for instance, the private investigator/journalist/lawyer will find a way to talk to an officer working on the investigation to tease out these details or figure out how to take a peek at the case file.

Here are the tasks that usually happen at the crime scene:

  • A responding officer(s) has to arrive and make preliminary observations.
  • The crime scene has to be contained. Once contained, a crime scene log is usually kept, detailing all those who have stepped inside the tape and into the scene.
  • A forensics team has to be called out and a thorough examination of the crime scene conducted. Crime scene photographers and videographers often document the scene before the fingerprint and trace evidence sweep is carried out.
  • Forensic analysis works on Locard’s Exchange Principle – every contact leaves a trace. Forensic evidence found at a crime scene can take many forms from DNA to trace evidence such as soil and cloth fibres.
  • If the crime is a murder, a medical specialist (usually a pathologist) has to be called out to certify death. That individual will also be prevailed upon to offer initial thoughts on Time of Death (TOD), and method of death.
  • Often, preliminary interviews are conducted at the scene with witnesses, those in the immediate vicinity, and the discoverer of the body. Further canvassing interviews might also be conducted with neighbours – though this may also happen later as a matter of routine in most police investigations.

Initial stages of the investigation

Most investigations start with a framing of the task ahead, where the law enforcement team assigned to the case meets to outline the actions that now have to take place in pursuit of the investigation, and to divide up responsibilities.

Other early steps include establishing the victim’s last known movements. This will throw up further interviews and avenues of investigation. Preliminary forensics will return and new lines of enquiry will open up, while others will be ruled out. By now various clues will be fighting for the team’s attention. For instance, if there is CCTV footage then that needs to be examined. Digital forensics is an increasingly large and resource-intensive aspect of modern investigations: laptops, phones, emails, social media analysis.

The main investigation

One of the distinguishing characteristics of Michael Connelly’s Harry Bosch series (my favourite crime novels) is the meticulousness with which Connelly depicts the investigative process. Bosch is shown going through the motions as he tracks down every piece of evidence and follows it through to its logical – and sometimes unexpected – conclusion. Connelly lingers over scenes describing Bosch going through documents and old records, or hunting down seemingly trivial bits of information. He builds the case gradually and we have a ringside seat for each step that Bosch takes. Connelly does this because he has a wealth of insider information at his disposal and a yen for accuracy.

I was lucky enough to meet Connelly at an event in London – we shared a UK publicist and she was kind enough to introduce us. Connelly was the Los Angeles Times crime reporter before becoming a full-time writer and he continues to maintain very strong relationships with the police department. He told me that he deliberately strives for procedural accuracy, partly because of the feedback he receives from active police detectives. One way you can see this is in the manner in which Bosch conducts suspect interviews. The aim of such an interview is to get suspects to talk. Contrary to TV depictions, few officers start such interviews by beating up the suspect. And the less said about ‘good cop bad cop’ the better.

Remember that the exact path of your investigation will depend on the type of protagonist you’re writing. The process should be organic to your character and the plot of your novel. And yes, there is still a place for gut instinct, for your protagonist to follow their own nose, even if it leads in a contrary direction to the evidence, even if it defies common sense, even if leads them straight into quicksand. After all, if your protagonist didn’t take charge of their own narrative every once in a while, it would make for a very dull story!

I’ll leave you with a quote from Joseph Wambaugh, former Grand Master of the Mystery Writers of America: ‘The best crime stories are not about how cops work on cases. They’re about how cases work on cops.’ In other words, it’s your character’s trial and tribulations, their narrative arc that will really bring readers along. Decide early on what is the unique persona, insight, skill, or approach that your protagonist can bring to an investigation that makes them worth following. If you can capture that you will have a lead that readers can’t help but want to spend time with. Always keep that in mind and you won’t go far wrong.

How do I find the information I need?

There is now so much information available online and in forensic/criminal investigation textbooks that you can readily get all the detail you need. That doesn’t mean it isn’t useful to pick the brain of an expert. They can touch off new ideas, new avenues to explore, and give you some granular detail about the day-to-day aspects of their work that you might otherwise not obtain.

So how do you do that? Some simple googling will throw up plenty of experts for hire. Consulting to the crime fiction industry is big business. Just be careful to pick someone with current knowledge. You can also write to police stations, lawyer’s offices, private investigators, university researchers, or journalists. Sometimes you’ll strike out, and sometimes you’ll have to buy someone lunch to get an hour of their time. You can also try to arrange visits to police stations or legal chambers. There are a number of mini-forensics courses that lead you through a mock crime scene. Writing a legal thriller? If you’re in the UK, you can go sit in the Old Bailey. It’s free and open to anyone.

Final messages

I cover a lot of the above material and much more in a six-module online course that I created for Curtis Brown called Writing Crime Fiction.

If you’ve found this useful you might want to join my newsletter. I regularly use it to post articles, competitions, giveaways, etc. In my next one I will include a rundown of all the different types of forensic evidence you might encounter during an investigation. You can join by clicking here:

And, of course, I’m going to encourage you to buy one of my books! If you might enjoy the richly evoked setting of India, with a strong emphasis on character and challenging puzzles, then my books might be for you. Buy from an indie bookshop, a book chain or online, such as here:

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