Texas Is Ahead of the Feds When It Comes to Forensic Science in Courtrooms

Texas Is Ahead of the Feds When It Comes to Forensic Science in Courtrooms
Thierry Ehrmann/Flickr

President Barack Obama's Council of Advisors on Science and Technology has a pretty clear-cut message to prosecutors across America: Stop convicting people based on junk science.

On Tuesday, the advisers released a scathing review of various forensic "science" practices that have, for some time, remained kosher in courtrooms — despite the serious lack of evidence proving their scientific validity.

Of the several methods reviewed, the only one the experts deemed trustworthy was your basic DNA testing, or analysis of simple mixtures of DNA when only two people's DNA is present. The other methods the council examined included bitemark analysis, complex DNA mixture analysis, footprint analysis like the kind you might see in some detective b-movie, microscopic hair analysis, firearms analysis and latent fingerprint analysis. And all of them were either in need of substantial improvement to be considered admissible in court or were considered basically useless.

Not necessarily a good look for criminal justice, especially when religious viewers of shows like CSI have been accustomed to trusting TV actors to catch the bad guys using these same fancy methods.

At least, however, there's some good news: Texas's own forensic science commission — which is not a common agency among all states — has already been studying these very issues in the past couple of years, and the White House findings mirror exactly what Texas experts have been saying.

"Texas has been really ahead of the curve in understanding that much of the pattern forensic evidence may be flawed," said William Press, vice chair of the council and a computer science and integrative biology professor at the University of Texas. "Texas is in a better position than most states to take the necessary steps to bring science into forensic science, and to make sure that we convict the right people."

The science and technology council's findings particularly line up with those of the forensic science commission on bitemark analysis, hair analysis and complex DNA mixture analysis.

The commission outright discredited bitemark analysis in April, recommending to all the state's prosecutors and judges to stop using it to secure convictions. The way it works is, forensic dentists examine a bite left on skin, for example, and compare it with a mold of a suspect's teeth. Forensic dentists have claimed for decades that the chance is slim to none that your bite marks are the same as anyone else's in the world — which is something both the president's advisers and the state forensic science commission have taken serious issue with.

As Tuesday's report notes: "Available scientific evidence strongly suggests that examiners not only cannot identify the source of the bite mark with reasonable accuracy, they cannot even consistently agree on whether an injury is a human bite mark."

Here's how that plays out in a trial: A forensic dentist told a Dallas jury in Steven Chaney's murder trial that there was a "one in a million chance" that the bite mark found on a dead person's arm belonged to anyone but Chaney. Turns out, Chaney was wrongfully convicted — based primarily on this testimony. He spent 28 years behind bars before being released last fall. At the time, Texas prosecutors and experts had reached agreement that bite mark analysis was junk.

“I think pretty much everybody agrees that there is no scientific basis for a statistical probability associated with a bite mark,” Dr. Henry Kessler, chair of the Texas Forensic Science Commission’s subcommittee on bitemark analysis, told us in April.

Texas has also particularly led the way in navigating major issues with interpretation of complex DNA mixtures. Last year, new advancements in DNA technology led forensic science experts to conclude that lab technicians may have been wrongly interpreting DNA mixture results (for example, if multiple people's DNA was present in a rape case) in thousands of cases dating back to 1999. In Texas specifically, more than 25,000 cases may need to be retested — because whereas before those forensic experts may have told juries there was a "one in a billion" chance the DNA could belong to another person, now experts believe it could be more like one in 38.

Still, despite the strides made in identifying questionable forensic science methods, Press said that Obama's science and technology advisers have already received negative feedback from prosecutors about Tuesday's report, presumably unhappy that the council is making it harder for them to secure convictions.

"It struck us as a little bit shocking, because every time you convict the wrong person, then the actual person has gone free," Press said. "It's hard to see how prosecutors would want to convict the wrong person. I think it's just that the law is a very conservative system, and change is very slow. But we feel that, by now, the scientific evidence is absolutely clear."


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