The Reality of Crime Scene Investigation. Part I: Common Myths

In a recent blog entry about forensic phenotyping, I wrote “Much of the information in these [crime scene investigation] TV shows is not exactly accurate. (I have long thought that I should write a blog entry contrasting forensic DNA laboratories as they exist on screen and in reality.)” It seems that someone has beat me to the punch. In his recent paper (1), Evan Durnal eloquently sums it up: “With this new style of ‘infotainment’, comes an increasingly blurred line between the hard facts of reality and the soft, quick solutions of entertainment.”

Durnal points out the single largest gripe that many criminal justice officials have about crime scene investigation (CSI) television shows: the common myths that are created and perpetuated by these types of TV shows. Durnal lists four main categories of myths: capabilities, roles and responsibilities, evidence and schedule. All of these myths are well known (and probably frustrating) to anyone who works in a forensic laboratory. Durnal also summarizes the effects of CSI shows on the judicial system, including jurors, prosecutors, defense attorneys, law enforcement officials and the criminals themselves. In part I of this two-part blog entry, I will present Durnal’s four categories of myths about crime scene investigation.

The first category, capability myths, refers to the fact that much of the science portrayed on CSI shows does not exist or is exaggerated. Modern forensic labs have amazing abilities and resources at their disposal to solve crimes, but TV producers are not satisfied with the reality. Maybe reality is not sexy enough, or there simply are not enough car chases and explosions? Durnal’s example of this type of myth is the omniscient database. On TV, it seems that databases exist for every possible product or material. In reality, these databases are restricted to information gathered and entered by law enforcement officials. There are huge databases for DNA (e.g., Combined DNA Index System, CODIS) and fingerprints (Automated Fingerprint Identification System, AFIS), but other examples of such universal databases are rare. In this same category is the perception that evidentiary samples require very little preparation before analysis. If you watch these types of shows, how often have you seen a forensic analyst put a blood-stained swab directly into an instrument, which then spits out the answer? Real science doesn’t work that way, not yet. Samples collected at a crime scene require preparation. For example, DNA needs to be isolated in most cases, and viscous, concentrated liquids need to be cleaned up and diluted before injection into a gas chromatography/mass spectrometry (GC/MS) instrument. However, such pre-analysis preparation is often tedious and boring, making it toxic to television ratings. No one wants to watch a scientist pipetting, diluting, vortexing, centrifuging and poring over data for hours. Yet, that is the reality.

The second myth that Durnal lists is related to roles and responsibilities. On television, forensic analysts are jacks-of-all-trades. They can perform DNA analyses, ballistic examinations and GC/MS and, in their spare time, they dabble in entomology, using insects present at the scene to assign a time of death. It appears that there is nothing these TV scientists cannot do. In reality, each step in processing crime scene evidence requires specialized skills, so forensic analysts focus their skills on one discipline, becoming an expert in that one area. For this reason, forensic analysts spend their time in the lab; they do not interrogate suspects or question witnesses. With rare exceptions, analysts do not visit crime scenes, leaving evidence collection to specially trained personnel. One of my favorite misperceptions in this category is that forensic analysts carry guns. Most do not. I have joked about this with some of my forensic analyst friends. Police officers on patrol carry guns for obvious reasons, but forensic analysts spend most, if not all, of their time in the lab—why would they need to carry guns? In case the deionized formamide “goes bad”?

I think lack of objectivity belongs in this category too. On TV, it seems that forensic analysts are privy to all evidence collected in a case, and as a result, form an opinion one way or another about a suspect’s guilt or innocence. In some cases, they develop elaborate schemes about how a crime was carried out to try to explain their results. In other words, they do not remain unbiased throughout the investigation. Real forensic analysts must remain objective. They report the unbiased results and cannot allow their personal beliefs to play a part in the analysis.

The third category on Durnal’s list is “evidence”, referring to the perception that criminals always leave enough suitable evidence to allow a crime to be solved. Despite continuing advances in forensic science that allow analysis of trace amounts of evidence, there are situations where there just is not enough evidence to solve the crime or the evidence that is recovered does not help resolve the case (e.g., a suspect’s DNA is recovered at a crime scene, but the suspect admits to being at the crime scene but denies participating in the crime). One negative effect of CSI shows is that criminals learn from them, and as a result, leave less incriminating evidence at a crime scene. Having said that, I feel that I have to add an observation here: I have heard plenty of examples where, despite a criminals’ best efforts to avoid leaving evidence behind or to clean up evidence after a crime was committed, enough evidence was recovered to allow a suspect to be identified and implicated. In many cases, law enforcement officials and forensic analysts still seem to be one step ahead of the criminals, and I think that is unlikely to change, considering the continuous advances in forensic science.

The final category is “schedule”, and I have to admit, these are the myths that annoy me the most. On TV, all crimes are solved within a 60-minute time slot, all database searches are done in a matter of seconds and all analyses are completed only minutes after they are started. I’ve worked in a lab, I’ve done PCR, and I’ve used some of the same chromatography techniques portrayed on these shows. There is a lot of preparatory work that gets glossed over or missed entirely on TV. Also, there are never inconclusive results. Everything works the first time; there is never the need to repeat an analysis. (Wow, I wish I had had that kind of skill/luck back when I was in the lab!) As Durnal points out “Good science can be extremely tedious and takes a great deal of time. It is paramount that the correct conclusion is reached, regardless of the time it takes.”

As you can see, there are a lot of myths being propagated by these TV shows, and those of us with science backgrounds realize that these television shows are not accurate. The directors do not claim that they are accurate. However, others with less science education and training may not recognize the disparity between TV and reality.

Be sure to watch for part II of this series, where I discuss Durnal’s summary of how the media’s portrayal of CSI TV shows is contributing to jurors’ unrealistic expectations in the courtroom and positively and negatively affecting the judicial process.

Do you work in a forensic lab or know someone who does, or do you have enough scientific training that you recognize (and are annoyed by) the inaccuracies? What are some of your favorite myths or inaccurate portrayals regarding science in CSI shows? Let’s generate a Top Ten list of “Reasons I Don’t Watch CSI Television Shows”. Add your suggestions for the Top Ten list to the comments field. I’ll start the list with another one of my favorites: Forensic labs on TV are always dark. Why is that?


  1. Durnal, E. (2010). Crime scene investigation (as seen on TV) Forensic Science International DOI: 10.1016/j.forsciint.2010.02.015
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Terri Sundquist

Terri has worked as a Scientific Communications Specialist at Promega Corporation for more than 13 years, and prior to that, spent more than 5 years solving problems and answering questions as a Promega Technical Services Scientist. She graduated with B.S. degrees in Chemistry and Biology at the University of Wisconsin—River Falls, then earned her M.S. in Molecular Biology from the Mayo Graduate School in Rochester Minnesota.


  1. Forensic labs on TV are always dark. Did someone forget to turn on the lights or pay the electricity bill? Do these jack-of-all-trades TV “superanalysts” have the ability to see in the dark, in addition to all of their other purported superpowers (e.g., ability to search a database faster than a speeding bullet and generate tall DNA profiles in a single bound)?

  2. On “House”, they sometimes use the Light Cycler (a PCR thermocycler) as a centrifuge. And the docs do the lab tests themselves.

  3. Even the fingerprint/palmprint databases can’t necessarily be categorized as universal, since each database is limited to its jurisdiction, and only stores prints for certain crimes. For example, while the FBI’s IAFIS database *does* cover the entire country, you aren’t going to find your jaywalkers in there.

    My employer (MorphoTrak) provides AFIS for both Miami Dade County and the Florida Department of Law Enforcement. If someone wanted to perform a comprehensive set of AFIS searches, that person would have to search the Miami Dade database and the FDLE database and the FBI IAFIS database. And if the print is of poor quality, it may need to be searched multiple times (again, using the boring pre-analysis preparation that you mentioned).

    There are some instances of multi-state databases – for example, the Western Identification Network AFIS (supplied by a competitor) covers eight states – but you still often need to perform a local search, a state search, and a national search if you want to get everything.

    The danger of simplification, of course, is that jurors assume that these techniques are incredibly easy to perform, and therefore should be performed. “Why didn’t you perform a DNA analysis of my purse that was snatched? You recovered the purse yesterday; don’t you have the DNA results yet?”

  4. Good point John.
    Databases exist at many levels, and a thorough search would require searches at all levels. A truly universal database would include local, state, national and even international information. Creating such a database would be a huge effort and require extensive discussions about what information is included and how that information is gathered and stored.
    Your comment about the danger of simplification is a good one and one that Durnal discusses in his paper (and I will be covering in part II of this series).

  5. All women in forensics are smokin’ hot and wear 6-inch stiletto heels, whether they’re chasing down a suspect with a Glock and a sterile swab or they’re setting up PCR reactions in the lab.
    Ok, so the smokin’ hot part is true…but the heels are definitely not up to lab safety standards.

  6. In your comments above regarding capabilities, you failed to mention the IBIS Ballistics Database. In addition, there are fairly large databases for shoe prints (Sole Mate) and tires treads.

    Please keep in mind that when you deal with a TV show (unless it runs in real time like “24”), you are not going to see everything that everybody does. No TV operates that way. Time does elapse on CSI but you do not have a clock to remind you of the passage of time. Also, you failed to mention that there is a lot of specialization on the CSI shows – not everyone runs DNA and not everyone carries out a ballistics match.

    It is true that CSIs rarely carry guns (some actually do) and are rarely first responders at a crime scene – leave that to SWAT and uniforms.

    Even on “Forensic Files” you do not see everything that is done in the lab. Watch and enjoy…Hal in Chicago

  7. I don’t know much about forensic science, but I’m fairly knowledgeable in computers, and on “Bones” there’s a program called “Angelator” which basically creates a 3d image into the air of any scenario the actress wants, so she just clicks a bunch of times on a remote control and boom, there’s suddenly a 3d video of a man stabbing another man in the air.

    Completely and utterly impossible in real life.

  8. Thanks for the comment Tarkinimene. I am not surprised: if Hollywood can’t get the DNA-related stuff right, we can’t expect them to get the computer stuff (or anything else, I suppose) right. These types of shows have some entertainment value, but for those of us with some knowledge of the reality, we’ll have to continue to suspend our disbelief while watching.

  9. I hate it when people that watch CSI try to compare it to Documentaries on Crime/Criminals.

    For example, A&E did a series on Serial Killers a few years back and one of America’s few Black Serial Killers was caught after they found Carpet Fibers on the bodies that they were able to match to a rare industrial carpet that had limited distribution.

    “See! All they needed to do was find a few blue fibers on the tape, run it through some process, and BAM! They got their guy!!! They went right to his apartment and got him! They could do CSI Stuff back in the 70’s!”


    They showed the process as super fast because it was a Documentary and they needed to tell the WHOLE STORY of this one serial killer in the span of an hour… Same way that a documentary on the Roman Empire needs to cram together as much info as possible since they have a limited time to impart information.

    The Green River Killer was active from 1982 to 1998 and Killed over 50 people yet the Final Report still only had an hour to talk about his crimes.

    Also, on shows like Law & Order: SVU they have a room with 10 Detectives all throwing information out into the air and EVERYONE in the room participates and they’re able to basically solve the crime just by talking things out amongst collogues… In a few seconds… Don’t those Detectives have cases of their own?? When was a crime as complicated as those portrayed on SVU solved by a Group Discussion amongst Collogues that all happen to be the best of friends?

    If cops could just sit down and talk out a crime and figure it all out from their desks, why are there any uncaught pedophiles?

    Not to mention how many times on these shows the Detectives go back to the scene of the crime to re-inspect the scene and magically find all sorts of evidence that the Technicians that are trained to collect missed…

    How did the Evidence Techs miss that Cigarette Butt? That blood and fluid coated hammer in the corner? Really? The DETECTIVES are the ones finding this evidence days or weeks after the crime then IMMEDIATELY use it to go after the Perp? The Detectives I know tend to do most of their “Detecting” from their desks…

    How about the way that none of the Evidence Techs in these shows are wearing any type of protective clothing? No shoe covers, no hair covers, on their hands and knees on the floor, practically rolling in the blood, distorting evidence and leaving their own contaminants left and right…

    “Dexter” shows up, gets down on the floor, looks around, and BAM knows exactly how the crime was committed… And usually by whom…

    If people can’t understand that these shows are FICTION, often times with reality factors on par with Stargate SG-1, they are morons and it’s just sad that criminals are getting set free because stupid people think that they should be given a Holographic Image of the criminal’s face after they feed the DNA Evidence into the computer before they’ll believe the guy is guilty.

  10. Thanks for explaining that it’s not really as simple as putting a blood stained item into a machine that spits out a result, because evidence actually requires a lot of preparation. I’ve recently started watching a lot of crime shows and was curious about how accurately forensic science is actually portrayed. I’m glad I read your article because it was interesting to learn about that inconsistency with actual science.

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