15 Ways CSI Got It Wrong

by | Dec 8, 2019

CSI, NCIS, Bones, Monk, Law and Order, Criminal Minds. All great TV shows full of drama and intrigue. But how accurate are they? I thought back on my 7 years as a forensic scientist in the DNA section of a state crime lab and compiled a list of some major areas where these shows fudged just a little and sometimes a whole lot. I also asked some crime scene colleagues of mine if they had anything to add (and they most definitely did).

Hopefully, this list helps you understand more about forensics and can help when you’re writing your books to make them more accurate. Fair warning! It’s a bit like learning a magician’s secrets. Once you know, there’s no going back. Read at your own risk!


Timing is by far the most inaccurate part of CSI and other crime dramas. Waiting for lab results, getting search warrants, and performing routine police work is dull and doesn’t move the story forward fast enough. They’ve only got an hour. (I do think this is where authors can fudge a little. But not too much.)


The people who perform the lab work don’t investigate the case. Detectives and investigators investigate; specially trained laboratory analysts perform analytical procedures.

Forensic scientists usually only specialize in one discipline. A DNA analyst doing firearms testing? Not likely. A document examiner doing toxicology analysis? Nope! I do know of a very small crime lab where the analysts perform both DNA and chemistry testing, but that’s an exception.

Certain lab positions on TV shows (usually played by quirky and lovable characters) just don’t exist. A few examples that come to mind are Garcia on Criminal Minds, Abby on NCIS, and Angela on Bones. Garcia never seems to need a search warrant and has access to every fake database ever, Abby knows too much about too many forensic disciplines, and no one except Angela can design/create/test random facial and bodily injury reconstruction software programs at the drop of a hat.


Oh, the tedium! Forensic science isn’t actually that glamorous or exciting. A big portion of the job is quite mundane. There’s mountains of documentation (AKA paperwork), excessive note-taking, meetings, and complex items/cases. I once had to test nearly a hundred stains on one item (bedding). Each stain had to be individually marked with the test result and documented in my notes. The screening test that I was performing took about 1 minute per stain, plus all the before/after procedures (quality checks, documentation of seal/label, and preparing/decontaminating my workbench and tools). It took me an entire afternoon to do one item. Is all the documentation and attention to detail super boring? Yes. Is it necessary? Absolutely. Quality control and transparency are imperative in forensic science.

Forensic Science is Always the Main Event

Forensic results are rarely the only evidence in a case. Forensics is part of a bigger picture. In my first year at the lab, my colleague testified in a double murder trial. A 15-year-old young woman and her 17-year-old boyfriend were accused of murdering the woman’s mother and stepsister. As part of my training program, I was required to observe her testimony. The trial lasted 6 days. My colleague testified for about 4 hours total. That leaves approximately 38 other hours filled with non-forensic testimony (assuming 7 hours of court each day). In addition to my colleague, I watched testimony from eyewitnesses, law enforcement, two delivery truck drivers who happened to observe the defendants’ getaway car on the interstate, and more.

Each case has its own path. Even if forensic results are obtained, the charges could be dropped, you could have uncooperative witnesses/victims, or the prosecuting attorney won’t move forward. I once did a homicide case with dozens of items (including a tailgate from a truck), only to have the defendant take a plea deal when the report was in tech review.

Forensic science might not be part of the case at all. Not all cases have items that need testing. I know of multiple cases that resulted in guilty verdicts without any forensic evidence.

You Always Get Results

Many crime dramas portray forensic science as the absolute answer that solves every case. Not all tested items yield positive results. The crime dramas show exactly the right evidence the characters need at just the right time with little to no effort, which never happens.

Unlikely Results

In addition to always obtaining results, the crime labs on TV always seem to get what can only be described as highly unlikely results. Fingerprints off a rock in a desert 14 years after the crime? I think not! For digital images, you can’t just zoom in and immediately get nice high resolution photo with a license plate. Most raw video footage isn’t great to start with, and getting an image off a reflection in a window or someone’s glasses is just plain ludicrous.

All Results Mean Something

Not all lab results are probative (especially in DNA). Am I going to get a DNA profile from a bloodstain on a homicide victim’s shirt? Yes. Is it necessarily going to belong to the suspect? No. Will I get a DNA profile from touch DNA on a swab from the front door of a bar? Possibly (Touch DNA is hit or miss). Will it be from the suspect? No. It will probably be a low-level mixture of 4+ people (see below). Will I get a DNA profile off a kitchen knife allegedly used by a husband to kill his wife? Yes. But the husband and wife live together, and that’s his knife in his kitchen in his house. The DNA results can be explained away.

Inconclusive Results

Sometimes the results from crime labs are inconclusive, which usually happens when there’s not enough information to form a conclusion either way. In DNA, this happens for certain types of profiles such as low-level partial mixtures with lots of people, every DNA analyst’s favorite. (Ha! These types of profiles are the worst.) The DNA results are inconclusive because even though a profile was obtained, the analyst can’t do much with it.

Blood Testing

I once saw an episode of CSI Miami where they sprayed luminol on a deceased victim in broad daylight. When using luminol to detect blood, the room or crime scene must be completely dark.

An alternate light source isn’t used to find blood. You can use it to find other body fluids (semen, saliva, and other bodily secretions), just not blood.

Lab Glassware

There aren’t beakers and flasks filled with random chemicals every color of the rainbow sitting around the lab. Are they pretty? Absolutely. Am I guilty of using photos like these on this website? Yes. But are they real? Nope. Most chemical solutions in the crime lab are colorless.

Types of Cases in DNA

TV shows usually focus on violent crimes. Murder, assault, arson, kidnapping and serial killers make for compelling television, but in DNA, there’s a whole slew of illegal activities that are rarely a show’s focus: property crimes. Over the course of my 7 years as a forensic scientist, these types of cases steadily increased in number until they were about half of our caseload by the time I left. Examples of property crimes include burglary, theft, robbery, and vandalism.

Types of Crime Labs

There isn’t just one big crime lab that performs every type of forensic test. Crime labs can be split into two general categories: traditional and specialized. Traditional crime labs generally perform DNA, controlled substances, firearms/toolmarks, fingerprints, toxicology, documents, digital forensics, and trace analysis. Other forensic disciplines that require specialized testing are anthropology, entomology, forensic genealogy, paternity, facial reconstruction, dentistry, and others. For more information about the different kinds of crime labs and how they work, click here.

Not So Fast, New Technique!

Brand new techniques developed on the spot are never used on cases (at least in traditional crime labs). Before results from a new scientific technique can be admitted into evidence in court, the technique has to be generally accepted in the scientific community, which happens over time, and requires a special hearing with the judge. In a crime lab, forensic scientists must follow very strict protocols and procedures that have been scrutinized and approved by accrediting agencies. Any deviations from these protocols (where allowed) are carefully documented.

Pictures in Databases

When a search is performed in a database for DNA, firearms, or fingerprints, matches don’t pop up in a few seconds with a picture of the individual and a last known address. In fact, these databases don’t have pictures of people at all. A search will return potential matches (with case identifiers only) that need to be verified by a qualified analyst. If a match is confirmed, a report with the relevant information is released to the agency.

Crime Scenes

I didn’t go to crime scenes at my old lab, but I know they’re a big part of crime fiction, so I asked some CSI colleagues of mine where TV crime dramas fudge a little (or a lot).

Let’s start with location. Most crime scenes aren’t at nice suburban locations or mansions in nice quiet neighborhoods. They’re in dirty alleys, unkept homes, outside in bad weather, and other unpleasant locations.

CSI personnel don’t wear stylish put-together outfits with high heels.

CSIs don’t find the evidence they need right away. You don’t walk right into a room, shine a flashlight around, and then quickly find the clue that solves the case. It’s meticulous, repetitive work. Everything has to be documented and then packaged and labeled. It can take hours or even days to go through a crime scene.

I see characters in TV shows just walk into a room and pick up evidence all the time. CSIs don’t pick up items without documenting them first. This can be done by sketching or taking a picture, along with taking notes. Real CSIs also use gloves to handle evidence, not pens or pencils.

CSIs don’t go through houses or locations in the dark if there’s electricity. They document that the light was off when they first arrived and then turn it on. It makes looking for evidence much easier (who knew?).

Forensic pathologists can’t tell cause or manner of death (or any number of other things) until they get the victim back to the lab and perform the autopsy and other testing. Taking a quick glance at the body and making a quick and dirty conclusion just doesn’t happen.

Access to crime scenes is limited. It can depend on the agency’s policy, but personnel that are present at crime scenes usually use a sign-in list, and access to the scene is restricted to certain people, such as responding officers, CSI techs and detectives. TV crime dramas often show any number of people wandering in and out at any given time.

Did any of these surprise you? If yes, which one? Did you know them all already? Are all TV crime dramas ruined for you forever? Let me know in the comments below!





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