How Scientific Is Forensic Science?

How Scientific Is Forensic Science? January 12, 2018


Forensic science, as used by investigators on police shows and lawyers in the movies, is embedded in our cultural imagination as a reliable and objective instrument for establishing guilt and innocence. However, it appears that we’re idealizing forensics, which rely much more on subjective interpretations and questionable analyses than we’ve been led to believe. Law enforcement is guilty of overstating the reliability of forensic techniques, and scientific rigor is lacking in investigations.

Guilty Until Proven Guilty

Public Radio International’s podcast Science Friday cast doubt upon the scientific worth of tests that the criminal justice system has touted as ironclad for decades. The National Academies of Sciences, Engineering, and Medicine has criticized the procedures, and the FBI admits that its use of forensic techniques is geared to serve the prosecution in the majority of cases. In the podcast, the host talked to skeptics like Suzanne Bell, professor of forensic and analytical chemistry at West Virginia University:

IRA FLATOW: Let’s talk about a general lack of science in some big areas of forensic science. Let’s go through some of these– for example, like bite marks. How good are bite marks, Dr. Bell, for evidence?

SUZANNE BELL: Well, I think they’ve been pretty well discredited to this point. The science or the underlying assumptions of bite-mark analysis was that A, human dentition is unique, and B, that when you make those marks in skin, the skin will reflect that uniqueness. And both of those have been pretty well disproven. It’s a subjective method.

What’s worse, the much-needed oversight process is in limbo because the multidisciplinary commission President Obama appointed to oversee the reliability of forensic science —the National Commission on Forensic Science— is now gone because the Trump administration let the commission expire.

Class and Punishment

There are many aspects to this issue, not only scientific ones. The guests on the podcast talk about the way forensics disadvantages low income defendants, who don’t have the resources or know-how to challenge law enforcement analyses of crime scene data. Judges are hesitant to allow experts to testify against the state’s evidence unless they know why there should be a question raised about it, which in turn is unlikely without the expert testimony itself. The socioeconomic consequences of over-reliance on faulty forensics and exaggerated expert testimony are too significant to ignore.

State’s Evidence

The podcast doesn’t mention the point that is most glaring here, which is our cultural idea that evidence is objective and sacrosanct. The National Academy of Science was cautious about causing alarm in its report linked above, but it described a situation where the variations in methods, rigor, and training in the various disciplines that make up forensic science make it impossible to portray the process of identifying the guilty as in any way precise or objective.

Like any other science, forensics is about inference, not evidence. We need to acknowledge that data can be interpreted in many different ways, that we should question our certainty about the assumptions underlying these supposedly airtight methods, and that science is a legitimating institution that serves to protect the powerful and validate their authority.

I highly recommend people listen to the 18-minute podcast for an inside look at forensics and justice.

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