Junk science in the courtroom

By Alan Bean

A feature length investigative piece in the Washington Post reports that FBI forensic experts regularly present overblown and inaccurate testimony at trial.  The problem is especially acute, the article suggests in the case of hair examination testimony.  When DOJ studies uncovered flawed forensic testimony, the article claims, the information was turned over to prosecutors and was often kept from defendants and their attorneys.

Here are some highlights from the five-page article:

A review of the task force documents, as well as Post interviews, found that the Justice Department struggled to balance its roles as a law enforcer defending convictions, a minister of justice protecting the innocent, and a patron and practitioner of forensic science . . .

Overall, calls to defense lawyers indicate and records documented that prosecutors disclosed the reviews’ results to defendants in fewer than half of the 250-plus questioned cases . . .

By excluding defense lawyers from the process and leaving it to prosecutors to decide case by case what to disclose, authorities waded into a legal and ethical morass that left some prisoners locked away for years longer than necessary. By adopting a secret process that limited accountability, documents show, the task force left the scope and nature of scientific problems unreported, obscuring issues from further study and permitting similar breakdowns . . .

Popularized in fiction by Sherlock Holmes, hair comparison became an established forensic science by the 1950s. Before modern-day DNA testing, hair analysis could, at its best, accurately narrow the pool of criminal suspects to a class or group or definitively rule out a person as a possible source.

But in practice, even before the “ ‘CSI’ effect” led jurors to expect scientific evidence at every trial, a claim of a hair match packed a powerful, dramatic punch in court. The testimony, usually by a respected scientist working at a respected federal agency, allowed prosecutors to boil down ambiguous cases for jurors to a single, incriminating piece of human evidence left at the scene.

[In one case, an expert] acknowledged that (test) results could rule out a person or be inconclusive. However, he told jurors that a “match” reflected a high likelihood that two hairs came from the same person. [The expert] added, “Only on very rare occasions have I seen hairs of two individuals that show the same characteristics.”

In [another case, a government expert] went further as he summed up the evidence. “There is one chance, perhaps for all we know, in 10 million that it could [be] someone else’s hair,” he said in his closing arguments, sounding the final word for the government.

In 2002, the FBI found after it analyzed DNA in 80 selected hair cases that its agents had reported false matches more than 11 percent of the time. “I don’t believe forensic science truly understood the significance of microscopic hair comparison, and it wasn’t until [DNA] that we learned that 11 percent of the time, two hairs can be microscopically similar yet come from different people,” said Dwight E. Adams, who directed the FBI lab from 2002 to 2006.

. . . [A] Post review of the small fraction of cases in which an appeals court opinion describes FBI hair testimony shows that several FBI agents gave improper testimony, asserting the remote odds of a false match or invoking bogus statistics in the absence of data.

The Post article focuses on hair comparison testimony, but other studies have raised grave doubts about expert testimony dealing with fingerprint, handwriting, polygraph, firearm, fire, and pattern and impression evidence.  In short, junk science in the courtroom is a major problem.  The DOJ is commended for reviewing the work of its own experts, but the repeated failure to inform defense counsel of the results of faulty tests is deeply disturbing.

Here’s the problem: for the past forty years, a mountain of legislation, at the state and federal level, has made it increasingly easy for prosecutors to secure convictions.  Until recently, there was little concern that policies greasing the wheels of conviction may also increase the number of innocent people going to prison.  DNA testing has demonstrated just how often the system gets it wrong.  The primary cause of wrongful conviction is confused eyewitness testimony; but expert testimony rooted in junk science is also a major problem.