Everybody loves those dazzling displays of forensics on Law and Order when Ice-T spots a hair at a crime scene and takes it back to the lab to process through the database containing the DNA of every single human on the planet. However, that's not how forensic science actually works. In fact, that kind of scenework assumes said "science" works at all, while in reality forensic methods are far from foolproof. Jurors (and even judges) have been falling victim to the "CSI effect" since procedural crime dramas rose to prominence in the early 2000s.
Forensics in real life compared to forensics on CSI suffer from a major discrepancy: while jurors generally accept such evidence as absolute fact in both cases, only in one is it absolute. It may seem cool when Mark Harmon determines the killer from a blood spatter, but such evidence is as subjective as a Rorschach test, only with much graver consequences.
That's why it's important to examine the dangers of forensic science brought about by the weird and fantastic cases on CSI (though sometimes real life can be stranger than fiction, as seen in these creepy forensic cases).
"Talking about science in the courtroom used to be like talking about geometry — a real jury turnoff. Now that there's this almost obsession with the [TV] shows, you can talk to jurors about [scientific evidence] and just see from the looks on their faces that they find it fascinating,”
said jury consultant Robert Hirschhorn in a 2004 USA Today story, as reported by LegalZoom.
For jurors enthralled with CSI and similar crime dramas, assessing DNA evidence is more than a review of dry science; it's a chance to live out the exciting lives of their TV idols. For just a moment, their "mundane" lives align with David Caruso's in a fantasy come true. Yet given the frequent unreliability of forensic science, it's more fantasy than reality in the real-world courtroom.
This isn't to say all jurors are merely TV-educated or have a taste for the dramatic. But the pervasiveness of forensics dramas have blurred, on whole, the idea of what counts as "expertise," and television production (by necessity) must do its share of cut-and-paste when it comes to depicting crime scene investigations.
Juries Have Unrealistic Expectations About DNA Evidence
“When you go to court, the jurors expect you to always have fingerprint evidence and DNA evidence on everything — even though that might not be an essential part of the investigation,” forensic scientist Sarah Owen told the Chicago Tribune. She went on to say:
“And if you weren’t able to get DNA results on something, that doesn’t necessarily mean that that individual is innocent. It just means that DNA wasn’t present. But [DNA evidence] may not even be necessary, because there’s other corroborating evidence through the investigations.”
"As recognition of DNA’s revelatory power seeped into popular culture, courtroom experts started talking about a 'CSI effect,' whereby juries, schooled by television police procedurals, needed only to hear those three magic letters—DNA — to arrive at a guilty verdict."
Shaer went on to detail a study done by a felony trial judge in Michigan, which found that 75% of local jurors surveyed expected DNA evidence in rape cases, almost half in murder or attempted-murder cases, and 22% expected DNA evidence in every criminal case.
There Are No Digital Systems That Process Forensic Evidence In An Instant
It's a common sight on any crime show: a detective looms over the shoulder of their spunky forensic scientist. The "expert," who's probably aggressively goth for some reason, has just scanned of a bite mark or fingerprint and is now processing it, running it through their database containing the name and dental records of every criminal on the planet.
“With large-capacity hard drives, it’s not uncommon to need as much as 40 hours to do a preliminary search,” forensic scientist John Briscoe explained to the Chicago Tribune. “TV dramas make it seem as if records can be searched and the case wrapped up in 30 minutes.”
Obviously, however, no such systems exist, yet jurors often expect those results. The existence of such technology (or even the perceived existence) makes forensic science seem infallible, but the reality is far more depressing.
Bite Mark Forensics Are Coming To Be Seen As Flawed, Often Resulting In False Convictions
According to the Oxford Journal of Law and the Biosciences, "The Texas Forensic Science Commission recently recommended a moratorium on the admission of bite mark expert testimony." And here's why: in 1997, William Richards was sentenced to serve 25 years to life for the murder of his wife in California. Even though three trials failed to provide enough evidence to convict him, a fourth trial introduced bite mark evidence, which finally swayed the jury.
After 19 years in prison, Richards's conviction was reversed, 10 years after the "forensic odontologist" recanted his testimony in which he said "the canine teeth made a 'pretty good alignment' with the husband’s teeth," but later admitted "he wasn’t even sure if the lesion on the victim’s hand was a human bite mark." Richards is not the only person to have suffered this fate, and it's increasingly clear that bite mark evidence is rarely scientifically valid.
Even Forensic Scientists Are Subject To Inherent Biases
Of course, jurors aren't inoculated from feeling confirmation bias vis-à-vis forensic science when the forensic scientist themselves are susceptible to such flawed thinking. Confirmation bias, simply put, means that humans have a tendency to interpret evidence in a way that reinforces or affirms already-held beliefs. Jeff Kukucka of the Huffington Posthypothesized this inherent human trait permeates both forensic science and its practitioners.
He pointed to the Madrid train bombings of 2004, in which an American Muslim man named Brandon Mayfield was detained after three FBI fingerprint experts erroneously concluded Mayfield's prints matched old ones on a bag containing a bomb. After the Spanish authorities identified and apprehended the real perpetrator, the DOJ’s Office of the Inspector General reviewed the case and found the FBI agents' “...'Loss of objectivity' led examiners to see 'similarities... that were not in fact present.'”
Forensic Scientists Are Very Vulnerable To Confirmation Bias
After the Madrid train bombings, Senior Cognitive Neuroscience Researcher and Harvard graduate Itiel Dror, Ph.D. and his colleagues devised a series of tests to determine if forensic scientists always reach objective conclusions. TL;DR: all scientists do not always reach objective conclusions. According to the Huffington Post:
"They presented five fingerprint experts with prints that, unbeknownst to them, they had deemed a 'match' earlier in their career. When told that these prints were taken from the Mayfield case, four of the five experts now concluded that they did not match, suggesting that their judgments were sensitive to context. In a follow-up study, Dror and David Charlton gave experts case files containing prints that they had (unknowingly) examined before, along with additional evidence that implied guilt (i.e., a confession) or innocence (i.e., an iron-clad alibi). When given this new information, experts changed 17 percent of their own prior judgments."
