Many of the “forensic science” methods commonly used in criminal cases and portrayed in popular police TV dramas have never been scientifically validated and may lead to unjust verdicts, according to an editorial in this week’s Proceedings of the National Academy of Sciences.
“We wanted to alert people that this is a continuing and a major issue: that many of the forensic techniques used today to put people in jail have no scientific backing,” says senior author Arturo Casadevall, MD, Bloomberg Distinguished Professor and the Alfred & Jill Sommer Professor and Chair of Molecular Microbiology and Immunology at Johns Hopkins Bloomberg School of Public Health.
The structure of the field of forensic science inhibits vital reforms. Almost all publicly funded laboratories, whether federal, state, or local, are associated with law enforcement. At the very least, this creates an inherent conflict-of-interest and leads to legitimate concerns of objectivity and bias. The linkage of forensic laboratories with prosecutorial entities dates back as far as 13th century China, was pervasive in Europe in the mid-late 19th century, and spread from there to the United States
Some forensic methods have been rooted in science. Medicolegal death investigation emerged from medical science, because death investigation was connected to the protection of public health. Techniques of analytical chemistry were applied to the certain types of evidence, such as seized drug analysis, toxicological analysis, and aspects of instrumental analysis applied to trace evidence. More recently, molecular biology gave rise to DNA typing to forensic applications.
The evolution of other forensic disciplines, particularly those related to pattern evidence, followed a different course, having been developed primarily within law enforcement environments or at the behest of law enforcement. Disciplines, such as fingerprints, firearms, and tool marks, blood-stain pattern analysis, tread-impression analysis, and bite mark analysis matured largely outside of the traditional scientific community during a time when admissibility standards for scientific evidence had yet to be formulated. Thus, admissibility of such evidence rightly or wrongly created judicial precedent in decisions that often did not—or could not—involve the level of research that would today be needed to establish scientific validity. Paper. open access – Suzanne Bell, Sunita Sah, Thomas D. Albright, S. James Gates, M. Bonner Denton, Arturo Casadevall. A call for more science in forensic science. Proceedings of the National Academy of Sciences, 2018; 201712161 DOI: 10.1073/pnas.1712161115 More.
Red what they have to say about DNA and fingerprinting evidence.
Also, re forensic handwriting analysis: Can estimates from forensic handwriting experts be trusted in court? From ScienceDaily:
“The overall error rate even for experts is large enough as to raise questions about whether their estimates can be sufficiently trustworthy for presentation in courts,” notes Martire. “We suggest that a cautious approach should be taken before endorsing the use of experience-based likelihood ratios for forensic purposes in the future.” Paper. open access – Kristy A. Martire, Bethany Growns, Danielle J. Navarro. What do the experts know? Calibration, precision, and the wisdom of crowds among forensic handwriting experts. Psychonomic Bulletin & Review, 2018; DOI: 10.3758/s13423-018-1448-3 More.
Historical footnote: In 2009, it came out that DNA evidence caused British Isles police to spend 15 years pursuing a phantom serial killer:
The only clues that “The Woman Without a Face” left behind at 40 different crime scenes were DNA traces. These were collected on cotton swabs, supplied to the police in a number of European countries. Now police investigators have established that in all probability the DNA had not been left by their quarry but by a woman working for the German medical company supplying the swabs, who had inadvertently contaminated them.
None of this involves deliberate manipulation of evidence, which has apparently occurred as well. Rather, over-reliance on the “power of science,” which likely stems from the public taste for cop shows in which such evidence is presented as irrefutable Fact is part of the pattern of complacency.
Reform largely depends on our willingness to let go of demands from science for false certainty.
We will deal with “lie detector” tests another time.
Added: Heather Zeiger writes to say,
Even if lawyers and forensic experts know about the error rates and false positives in DNA testing, they still have to deal with a jury, most of whom have seen shows like CSI. It is much harder to convince a jury that their favorite narratives aren’t how things actually work in real life. If one lawyer says, “look, this is what the scientists say” and the other lawyer says, “this is not conclusive” people are going to believe the scientists.
Here’s an interesting article from The Atlantic on this issue. It re-iterates what the UD post says. This is part of a trend where there is too much confidence in DNA studies, whether it is commercial genetic tests or forensic tests. It is as though we forget the human factor in collecting evidence, or the fact that these tests are not always conclusive.
Note: Zeiger (@hzeiger) has also written on blind faith in DNA:
Then there is the problem of the technique being too sensitive to the point that much is made over very little evidence. One example mentioned by The Atlantic was the case of Lukis Anderson, a homeless man in California with a history of non-violent crimes. He was implicated in the murder of a millionaire at his mansion because some of Anderson’s DNA was found under the millionaire’s fingernail. It turns out that Anderson had been taken to the hospital earlier that day by the same paramedics who picked up the millionaire. The same oxygen monitor had been used on the fingers of Anderson and the victim. More.
Goof-ups in science are still goof-ups. And they can have serious consequences.
See also: Flawed forensics: DNA analysis is NOT The Truth, as in endless cop show reruns
Forensics files: What? We can’t trust forensic science?/a>
Forensic DNA evidence in doubt? (low copy analysis)
Is forensics really a science.? Yes, and it suffers from the same problems as any other.