Juries Should Accept Testimony "With a Grain of Salt"

The Washington Post yesterday published an article (from which the above graphic was drawn). I quote from its lead paragraph:

The Justice Department and FBI have formally acknowledged that nearly every examiner in an elite FBI forensic unit gave flawed testimony in almost all trials in which they offered evidence against criminal defendants over more than a two-decade period before 2000.

 The FBI has spent decades seeking to establish a reputation for expert analysis of evidence and fairness in the presentation of its results. The halo effect on juries is not accidental.

Is fingerprint identification accurate and reliable? Here is a quote from one source:

The handful of studies of fingerprints show a troubling pattern of errors. Since 1995, Collaborative Testing Services, a company that evaluates the reliability and performance of fingerprint labs, has administered an annual and voluntary test. It sends fingerprint labs a test that includes eight to twelve pairs of prints that examiners confirm or reject as matches. The pairs usually consist of complete, not partial prints, making identifications easier than the real situations examiners face. Nevertheless the error rate has varied from 3% to a dismal 20%. 

Equally troubling is a test conducted by the FBI. During Byron Mitchell’s trial for armed robbery in 1999, his lawyers questioned the reliability of fingerprint identifications. In response, the FBI sent two prints taken from the getaway car and Mitchell’s prints to 53 crime labs to confirm the agency’s identification. Of the 39 labs that sent back their results, 9 (23%) concluded that Mitchell’s prints did not match those from the car. The judge nevertheless rejected the defense’s challenge and accepted the fingerprint evidence. Mitchell was convicted and remains in prison. The FBI has not repeated the experiment.

Lie Detector tests were once used widely by police and as evidence in courts. Here is what one source says about them:

In past times they were often used by police and government agents to interrogate suspected criminals, but as they have been proven to be extremely unreliable indicators of lying, their use has lessened in recent years (usually because of court rules prohibiting their use).

How about eye witness testimony? I draw this from an American Psychological Association website:

"Like trace evidence, eyewitness evidence can be contaminated, lost, destroyed or otherwise made to produce results that can lead to an incorrect reconstruction of the crime," he says. Investigators who employ a scientific model to collect, analyze and interpret eyewitness evidence may avoid incidents like Olson's potentially flawed identification of the Fairbanks suspects, he notes. 

In fact, Wells says that other evidence techniques, such as police lineups, are similar to scientific experiments. In lineups, the police have a hypothesis, they provide instructions, collect responses and interpret the results. As such, the same factors that can bias the results of an experiment can bias an eyewitness's performance in picking suspects out of a lineup, he says. 

In a 2000 American Psychologist (Vol. 55, No. 6, pages 581-598) article that dovetailed with the Department of Justice report, Wells and his colleagues outlined a number of ways police can avoid biasing eyewitness testimony, including warning the witness that the actual perpetrator may or may not be in a lineup, maintaining a double-blind lineup environment so that a detective cannot influence a witness's judgments and securing a statement of the witness's certainty of their identification. 

"To a research psychologist, the changes seem obvious," he says. "But to law enforcement officials they are very different from how they've tended to do things in the past."

I wonder how many jurors understand that testimony that they hear in court, even expert testimony, may not be accurate. How many are prepared to recognize that even FBI testimony may be flawed and may not in itself "prove" culpability.