The Reality of Crime Scene Investigation. Part II: The CSI Effect in the Courtroom

Judge talking to a lawerIn a recent paper, Evan Durnal from the Criminal Justice Department at the University of Central Missouri listed common myths that are created and perpetuated by crime scene investigation (CSI) television shows and summarized the effects of these shows on the judicial system (1). In part I of this two-part blog entry, I presented Durnal’s four categories of myths about crime scene investigation. In part II, I discuss the effects of these television shows on the judicial system, including jurors, prosecutors, defense attorneys, law enforcement officials and the criminals themselves.

In his paper, Durnal lists four main categories of myths: capabilities, roles and responsibilities, evidence and schedule. These myths all influence jurors’ expectations in the courtroom and affect the roles, responsibilities and tactics of judges, attorneys and law enforcement officials. Durnal describes it thusly “Nearly all definitions of the [CSI] effect stem from and refer to the impact that CSI and related shows have on the ability of trial juries to objectively hear testimony and make decisions without biasing those decisions on information obtained outside the courtroom proceedings”. He lists a number of examples demonstrating the CSI effect, originally published by Willing (2), including:

  • In Richmond, Virginia, jurors in a murder trial learned about a cigarette butt found at the crime scene, but when no DNA evidence from the cigarette butt was introduced during the trial, asked the judge whether DNA testing had been performed. Defense attorneys had ordered DNA testing but had not yet introduced it into evidence. The tests exonerated the defendant, and the jury acquitted him.
  • In Phoenix, Arizona, jurors in a murder trial alerted the judge that a bloody coat found at the murder scene and introduced as evidence had not been tested for the presence of DNA. However, DNA testing was unnecessary in this case because the defendant admitted to being at the crime scene. The jurors knew enough about forensic science to want to see DNA results but could not determine when DNA testing was appropriate.
  • In Wilmington, Delaware, in a series of simulated trials being conducted by federal researchers, one juror who was faced with especially complicated DNA evidence complained that analysts never encountered such problems on CSI.

Watching CSI shows can influence people’s perceptions about what forensic tests are important and appropriate and the weight of scientific evidence, as well as their expectations as to the amount of scientific evidence recovered from a crime scene, especially for more serious crimes such as rape and murder. On television, there is always plenty of evidence to identify a criminal, analysis results provide conclusive answers in every case and there are rarely unsolved cases. We want this to be true in real life too, but it is not.

Increasingly, prosecutors and defense attorneys have to deal with these perceptions and expectations. Attorneys spend more time educating jurors about the proper applications of certain techniques and the reality of forensic laboratory capabilities. They must explain not only existing evidence but also why certain evidence does not exist. Prosecutors in some states are even employing “negative evidence witnesses” to make the point that not all crime scenes yield DNA, fingerprints or other evidence. Attorneys face jurors with exaggerated faith in forensic evidence, jurors who expect black-and-white answers of “Yes” and “No” without the gray areas of “Maybe” or “Similar”. Defense attorneys and prosecutors are spending more time assessing potential jurors (and their TV-watching habits) during jury selection to identify those who might be overly influenced by CSI shows. As a result, trials take more time. Also, more prosecutors are walking away with acquittals in what were once considered routine cases.

The CSI effect extends to judges, who must ensure that trials are fair. To do so, they need to identify and manage any potentially misleading evidence. However, the CSI effect can be a formidable source of bias, and judges often must spend more time on jury instructions to try to minimize this effect. Judges are becoming more educated about forensic science so that they can recognize when the CSI effect is creeping into the courtroom.

Even criminals are not immune to the CSI effect. Although CSI shows are not exactly accurate in their portrayal of forensic science, many techniques shown on TV have a basis in reality, and criminals can benefit by watching CSI shows to learn how to cover their tracks more effectively. Criminals learn to clean crime scenes with bleach to destroy DNA and wear gloves to avoid leaving fingerprints. This means that law enforcement officials must work harder and submit more physical evidence for analysis. This puts a strain on existing resources to catalog, store, track and analyze the additional samples. With this influx of samples, it is no wonder that many forensic labs are experiencing backlogs.

One good thing to come from the CSI effect is that there is an increasing number of students interested in forensic science. These television shows portray forensic analysts as sexy and cutting-edge with a passion for truth, justice and honesty. Scientists are no longer stereotyped as middle-aged, grayed-haired, bespectacled men in a white lab coat. Unfortunately, many CSI fans enter a forensic science program with a simplified view of what is required of them and an underestimate of the amount of training and preparation required to process samples and interpret complex results. Forensic science teachers have had to adjust their teaching styles accordingly. For example, teachers are now introducing exercises to teach students that not all crime scenes yield enough evidence to solve a crime and that some results can be inconclusive or even contradictory.

Durnal’s paper reminds me that science is not immune to the influence that television and other forms of media has on us and our views. I might even argue that the media’s influence on science can be particularly strong, as individuals without a strong science background might not realize the extend to which Hollywood exaggerates the truth and accept CSI and other science-related shows as more reality than fantasy. While science is progressing in leaps and bounds, I think we have a ways to go before an analyst can place a swab with a single drop of sweat into a mass spectrometer with no sample preparation, generate a full DNA profile and identify a perpetrator through a database search all in a matter of minutes. For now, we should remember one thing that our parents taught us: “If it sounds too good to be true, it probably is.”


  1. Durnal, E. (2010). Crime scene investigation (as seen on TV) Forensic Science International DOI: 10.1016/j.forsciint.2010.02.015
  2. Willing, R. (2004) ‘CSI effect’ has juries wanting more evidence. USA Today Accessed June 10, 2010. This can be viewed at:
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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. One good thing that has come from the CSI Effect is that the scientific testimony has become more “interesting” to the jurors. They seem to be more likely to have a general understanding of the science being discussed and look forward to the forensic science part of the trial.

  2. i like the data given in your site , i want to get the information regarding to the EFFECT OF THE FORENSIC LABOTORIES ON THE RATIO OF THE CRIME IN THE DEVELPING COUUTRIES .please guide me how can i get this or you can provide me . thank u so much

  3. zumrad, thank you for the positive feedback.
    I am not aware of any such studies in developing countries, but a quick search of the scientific literature revealed quite a few articles that might be of interest to you. For example, I searched High Wire Press with the keywords “crime laboratories developing countries” and got 3846 articles. I recommend that you visit High Wire Press ( or PubMed (, where you can perform a search of the current literature and find the articles that are most interesting to you.

  4. Terri,

    Just a low level war story to emphasize your point:

    When I was a patrol sergeant, a call came in of a burglary in progress downtown. I was mere blocks away, doing some paperwork in my car. The caller stated that the suspect smashed out the window of a business, reached inside and stole some of the shoes on display. I arrived with fifteen seconds of the call. As I pulled onto the street, I spotted the caller on his cell phone. He pointed across the street to the parking lot, where I saw a single figure standing with his back to me in the center of the lot. No one else was even on that side of the street. The suspect was about twenty yards from the broken window.

    I contacted him. He was a habitual pain in the ass that I recognized on sight. He saw me, dropped a pair of shoes he was holding and tried to run, but I grabbed him. He had glass shards on his clothing, shoes and shoe-related items on his person and there was literally a trail of discarded shoes from the broken window to where he was standing when I saw him (and remember, when the witness pointed him out).

    When I cuffed him, he said, “I didn’t do it. The window was broken when I got there.”

    During subsequent interrogation at the scene (all in line procedurally and admissible at trial), he admitted to taking the shoes from the window display.

    The witness not only positively identified him as the guy he saw break the window and take the shoes, but testified that he saw the entire act and kept the suspect under surveillance until I arrived AND I contacted that same guy.

    So it would seem to be a slam dunk case. It went to trial because the suspect had so many points from previous convictions that he had nothing to lose. At trial the defense attorney wanted to know the distance from where the witness was standing to the broken window and also the suspect’s location when I contacted him.

    I told him the downtown city street there is three lanes across and the witness was about 1/3 of a city block from the event when he witnessed it. The witness’s own testimony corroborated this. I even gave a distance estimate, plus or minus ten yards.

    The jury hung.


    Because two jurors were upset that we “did a piss poor job” of investigating the crime scene. What was “piss poor”? Well, we didn’t EXACTLY measure the distance from the witness to the window and the witness to the suspect I contacted.

    I kid you not.

    Now, I’m heartened that ten jurors were livid at these two morons, but it was still enough to hang the jury. Yeah, it was a penny ante burg, but the fact is that the inflated expectations that civilians who become jurors have sometimes get in the way of simple, common sense justice.

    Anyway, when I read your article, this story came to mind. It happened in about 2003, so I imagine the phenomenon is even greater today.


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