When writing is a crime – tips from a real CSI

I was very chuffed to be contacted by a real CSI recently who pointed out a ‘minor error’ in my literary thriller, The Peace Garden. Apparently I said a detective took some fingerprints, whereas it’s supposed to be a Crime Scene Investigator. He said it was a small error and that it didn’t impact on his enjoyment of the story as a whole which he describes as ‘a wonderfully well-crafted book’. But I’m glad he told me and I will be sure to correct it in the next edition. However, it got me thinking: what other common errors do writers commit when writing crime for book or screen? CSI Trembling has been kind enough to put together this guide:

I have been involved in criminal activity for over ten years now. No, that’s not a confession – I work as a Crime Scene Investigator (or Scenes of Crime Officer in old money!). I also read crime fiction, watch crime dramas on TV, and have written a crime novel. And, as a CSI, many of the things I see or read make me cringe! Sometimes good writing is let down by a poor appreciation of what real crime scene investigation is about. So, for the benefit of any aspiring crime writers, here are a few pointers.


Not all detectives have alcohol or relationship problems! Certainly show your character as flawed and human – but avoid the clichés.


Fictional detectives often work in teams of two. From a writer’s point of view, that’s an excellent device. It gives you a ready-made vehicle for developing characters and revealing information. The problem is that (in Britain at least) police forces don’t work that way! A major crime such as murder will have a number of detectives allocated to it. Typically there’ll be a Detective Chief Inspector as SIO (Senior Investigating Officer), with a variable number of Detective Inspector(s), Detective Sergeants and Detective Constables working on the case. There’ll also be specialists coming in at various times to add their input. It’s a team effort. The Prime Suspect TV dramas are quite good examples of how a murder investigation is managed – though bear in mind that the DCI in charge will probably be overseeing several operations at once.


Police forces all do much the same thing – but sometimes in very different ways. Not so much of a problem if your story’s about a fictional force, but if you’re writing about a real one, make sure you check the details.

The Crime Scene

How many times have you seen this on TV? The detective wanders into the crime scene, pulls on a pair of gloves and recovers the crucial piece of evidence. The problem with this is that, in real life, the detective has just rendered that evidence worthless! Entering a major crime scene without proper forensic clothing means potential cross-contamination, which means that all evidence recovered is open to challenge in court. Of course, it does happen – most CSI’s could tell you some horror stories about that – but if that’s how you write it, beware of the implications!


This is probably one of the most common areas for making mistakes. To put it simply, you can’t find fingerprints on just any surface – no matter how badly the plot needs it! Smooth, shiny surfaces such as glass and metal are good for fingerprints. Paper, cardboard and plastic bags will respond well to chemical treatment in the lab. But bear in mind that weather conditions have a considerable affect, and some surfaces (unpainted wood, rusty metal or most fabrics) will be unlikely to retain any marks at all.


The effectiveness of DNA recovery has increased dramatically over the years. If your suspect has drunk from a bottle or left behind a tool then there will probably be a much better chance of identification from DNA than fingerprints. In one murder / arson case I read about recently, DNA was recovered from a petrol can. But there are still limits. Recovering an offender’s DNA from a body, for example, would be unlikely unless there’s actual blood or tissue present (such as under the nails, from scratches).


Or, to be more accurate, footwear marks – since in the UK people don’t often go around barefoot! A lot can be learned from a good footwear mark, but (surprisingly, perhaps) not the size of the shoe. The reason being that in normal walking our feet don’t make complete and even contact with the ground. So it’s rare to find an exact and perfect mark. However, there are thousands of different tread patterns, so there’s a good chance of matching a mark to a specific type of shoe, boot or trainer. Moreover, since we all walk slightly differently, the wear pattern on the tread is distinctive. An expert can often say quite definitely that this shoe made this mark. But keep in mind that analysis to that level can’t be done by the CSI or detective at the scene – and you do need the suspect’s footwear for comparison.

These are just a few indications of the most common problems. As with any other writing – do your research!

Paul’s novel ‘Can of Worms’, is a crime thriller based on his own experience as a Scenes of Crime Officer. It’s available in Kindle format, or as a paperback. He has also written a number of short stories, mostly in the fantasy genre.
Paul Trembling’s blog.
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Related posts:

  1. Writing a series: tips from Ruth Downie
  2. Writing historical crime novels – interview with R.S. Downie
  3. Grave Tattoo on Crime Award Longlist
  4. Tips from a ‘generalist’ freelance writer

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9 comments on “When writing is a crime – tips from a real CSI

  1. Strauss de Jager on said:

    Hi Fiona, good to hear from you, and I do like your site. We recently had a break-in after 29 years of carefree living in good-old-Grahamstown. They scanned the house in minutes, and just took my laptop. After 5 days the police called to tell me it had been found (must also mention I asked our people at church that Sunday to pray it would be found). A couple from another African country was caught at PE Airport with 35 stolen lappies in their luggage!

    Coming back to your story, the CSI who came to investigate, told me he “lifted” a few good fingerprints. Suppose that’s another technical term to check out.

    Keep up the good work!


  2. Fiona Veitch Smith on said:

    Hi Strauss,

    Good to hear from you too! I’m so glad you and the 35 other people got their laptops back. One has to wonder about the intelligence of the crims to try to get 35 laptops through airport security. But hurrah for the SAPS!


  3. Paul Trembling on said:

    ‘Lifting’ is one of the most common means of recovering fingerprints. Essentially it means that a fingerprint (or palmprint – also identifiable) is developed with fingerprint powder, then a strip of clear sticky tape (like sellotape, but more transparent – and more expensive!) is placed on top. When the tape is ‘lifted’ the fingerprint comes with it. Well, normally it does – you do get some problems at times). The tape then goes onto a sheet of clear acetate which is endorsed with the relevant details and eventually sent to the Fingerprint Expert to examine.

    There are other methods of recovery – photographing, for example – and some forces may use those in preference, but lifting is the most common.

    Glad to hear you got your laptop back, Strauss!

  4. Fiona Veitch Smith on said:

    How would the CSI know which prints to lift from the laptop, Paul? Mine is covered with prints! Would they just lift all of the viable ones and then eliminate the owner?

  5. Paul Trembling on said:

    Exactly right, Fiona! Sometimes you can be fairly sure that the fingerprints were left by an intruder – if, for example, they’re clearly on the window frame climbing in!- but in most cases, we have to take any good marks on relevant surfaces (what the offender has touched or might have touched) and also take elimination print from the owners (often referred to as the ‘IP’ or Injured Party, but that usage varies from place to place).

  6. Fiona Veitch Smith on said:

    Well that explains why the burglar who literally kicked down my door and ransacked my entire house in Good old Grahamstown was never caught. The CSI took prints but never bothered getting any from me. One also wonders why it took a week for the police to ask the neighbours whether they had seen anything. One of them said: ‘Well I did see someone kicking a door in …’. ‘Did you call the police?’ asked the detective. ‘I didn’t think to,’ said the neighbour. Sigh.

  7. Paul Trembling on said:

    Unfortunately, the reality is that we can’t guarantee a result every time. Of course, most prolific burglars get themselves caught eventually, but that may be small comfort for the victim!

  8. Fiona Veitch Smith on said:

    Don’t get me started on the time I was attacked by a knife wielding lunatic who later walked past the station as I was busy making a statement and despite me pointing her out, she still wasn’t caught. Deep breaths, Fiona. This of course was not your police force, Paul 🙂

  9. Paul Trembling on said:

    It can happen anywhere, unfortunately. Some forces are better than others, but they’re all made up of human beings! Bring on RoboCop!

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