One of the most contentious topics we would discuss when I was studying for my forensic science degree was TV shows and movies involving some type of crime scene investigation. As forensic science students, we would relish knowing when a show depicted something inaccurate. We would also be ecstatic when we discovered a show portraying something accurate and true to our textbooks and teachings!
Legal professionals, in particular, tend to complain that what's depicted in film and TV has a significant impact on real people serving on juries in actual cases. They worry that if a case lacks the kind of proof seen on TV, jurors will conclude, "Well, it's a weak case!" And some cases may have been thrown out entirely.
Let's look at some of the most notable flaws and inaccuracies in these popular shows.
Dexter (Season 1, Episode 2)
There are so many moments from Dexter's eight seasons that I could pick out, but one thing that always stands out to me is the "stringing and reconstruction." For a start, you'd never do that kind of reconstruction/stringing for arterial, gushing, or cast-off patterns. Having a lot of strings in and around a crime scene is extremely inconvenient to other people at the scene as well as disturbing any other evidence in and around the crime scene. That's why this method is rarely used to this day! These days, we use 3D laser scanning technology to accurately depict the relational aspect of each piece of evidence, including blood splatters, so the investigators can rebuild and reconstruct crime scenes whenever they need to.
At the end of those strings, the blood spatter appears to be the result of someone throwing a pail of red paint on one wall and then squirting blood on another wall randomly. These cast-offs don't appear to be realistic because they look rather linear (presented in straight lines) and they're extremely similar to each other. In this scene, Dexter confirms that he knows that the weapon is a knife when realistically these cast-offs could have been caused by any sharp object.
Like its film series predecessor Shaun of the Dead, Hot Fuzz is a buddy comedy masquerading as a genre pastiche; however, part of me just can’t forgive this scene in particular. There are just too many fucking people at this crime scene! Although, after watching it multiple times, I think this was just Edgar Wright's way of putting as many cameos in one scene as possible—so I'll let this one slide!
The fewer people who come into contact with the crime scene, the better. This allows us to follow one of forensic science's basic principles: every contact leaves a trace. Whenever two items come into contact with each other, a material exchange occurs, which is why you wouldn't answer your phone inside the crime scene! You don't want hairs, fibers or DNA from your phone to get into the crime-scene and you don't want things from the scene to get onto your phone. This can cause contamination, which could lead to you being in the firing line in the courtroom and could either cause a whole case to be dismissed or worse could lead to you being wrongly convicted of the crime!
Nevertheless, this clip shows that they are wearing traditional forensic suits and gloves, eye protection, and face masks (before they became part of everyone’s everyday look!).
Then enters Simon Pegg, who isn't dressed in anything really resembling a crime-scene suit! Realistically they probably would not have allowed Simon Pegg to enter that scene without wearing personal protective equipment (PPE). Plus, an officer is normally stationed at the entrance with a notepad to record the identities and timestamps of everyone who enters and leaves the crime scene. This officer can then tell those people that by accessing the crime scene they are potentially contaminating it and are taking note of their identity in case the crime scene investigators need to collect DNA or other evidence.
CSI Miami (Season 11, Episode 5)
In this scene, we see a forensic analyst using Luminol, which is commonly used in the forensic industry, but not for the reason they're using it here. Luminol is used to locate blood traces after crime scenes have been cleaned up. It isn't used on evidence where there's significant blood and DNA.
The issue with using Luminol in this way is that the more you spray onto a surface, the more the stain will dilute. This makes it incredibly difficult for a DNA analyst to collect the white blood cells essential for DNA analysis. This is exactly what happens towards the end of this scene.
The Dark Knight
The Dark Knight's evidence recovery process is quite realistic because with cases that involve a firearm the CSIs can cut out a part of a wall for further examinations at a lab. However, the actual analysis phase when Bruce and Alfred discover a fingerprint on the bullet itself which is physically impossible, though we can recover prints from cartridges or casings. The rifling in the barrel will leave marks on that bullet that would strip a fingerprint clean off the actual bullet although a fired cartridge casing can retain prints, just like any other flat surface.
Let's have a look at it in more detail:
The cartridge case is made of brass or a similar soft metal that gets extremely hot when fired. When a gunman loads a cartridge into their gun, tiny quantities of salty sweat from their fingers are transferred onto it, recording an impression of the fingerprint. Firing the gun rapidly heats the casing, vaporizing the water in the sweat and leaving what we call non-volatile salts.
At high temperatures, those salts are molten, and you get a chemical reaction with the metal. Those reactions chemically etch the fingerprint into the surface of the bullet casing when the cartridge is fired, and no amount of washing or wiping will remove it!
Not so with the bullet, though. You wouldn't be able to recover a fingerprint just by scanning a bullet in this scenario, you would need the casing, instead. But I digress because who doesn't love Batman's detective side?
The amount of documentation associated with police and forensic procedures is consistently downplayed in crime dramas. But one show is getting that part right. Though Brooklyn 99 is classified as a comedic sitcom, it does an excellent job of hinting at how much paperwork investigators have to deal with. Any forensic or law enforcement professional will tell you that filling out endless amounts of paperwork and making sure documentation is up to date is the majority of their job. It isn't all just dead bodies and blood splatter!
The good news is that in spite of any differences between television and real life, interest in the sciences (and forensic science, in particular) has grown since these shows started airing. Although some students need to consider if they are willing to labor until 2 a.m. with a pair of tweezers plucking blowfly larvae off a corpse! And trust me, I’ve been there!
Did the accuracy/inaccuracy of any of these surprise you? If yes, which one? Did you know all this already? Are all TV crime dramas ruined for you forever?