Advances in forensic technology are showing that what used to be considered clear-cut proof of guilt may be nothing of the kind. A California case highlights a growing problem facing courts: what to do when an expert witness changes his mind because of better science and technology.
William Richards was convicted of brutally murdering his wife and is serving 25 years to life. The evidence against him was mostly circumstantial and two different juries were unable to reach a verdict. A third trial was aborted because the judge recused himself.
But at the fourth trial, the San Bernardino County prosecutor introduced for the first time testimony about a lesion on the victim's hand. Forensic dentist Norman Sperber analyzed an autopsy photograph during the trial, pointing out marks that appeared to be spaces between the teeth of someone who had bitten the victim.
Sperber told the jury that the apparent bite mark matched William Richards' unusual dental structure — one so unique he estimated just one or two out of 100 people might have it.
Richards was convicted in 1997. Ten years later, another forensic dentist corrected a distortion in the picture using photo-editing software.
"If I had known that technology would help me be more accurate, I definitely wouldn't have testified as I did," Sperber says. He now believes Richards could not have made the bite mark and questions if it's even human.
Old Cases, New Questions
Similar cases are arising around the country. Defendants have been exonerated or received new trials in Wisconsin and Texas. Last summer, the U.S. Department of Justice began reviewing thousands of convictions because of flawed forensic evidence.
In California, the state Supreme Court denied Richards' request for a new trial, saying that Sperber's new analysis a decade after the trial didn't "unerringly point" to Richards' innocence.
Jan Stiglitz, Richards' attorney and co-director of the California Innocence Project, says the court set an impossibly high bar.
"We know that the linchpin in this trial was the bite-mark evidence," she says. "We now have experts who have come forward and all said this is not a mark that was made by Richards' teeth. And yet Richards is going to spend the rest of his life in prison because he can't affirmatively prove that he didn't commit the crime."
But Jan Scully, past president of the National District Attorney's Association and district attorney for Sacramento County, takes a different view. "We need to have finality of verdicts," she says. "There is always a new opinion or there might be a refinement in our forensic science areas. So, just because something new occurs doesn't mean that the original conviction somehow was not valid."
The district attorney's office in San Bernardino, which prosecuted the original case, refused to comment for this story.
As more studies highlight major flaws with forensic evidence, challenges to convictions will continue to arise, says Georgia State University's Jessica Gabel. She says criminal appeals usually involve a so-called battle of the experts.
"But when you've got the expert who testified for the prosecution, who comes back and revisits the evidence and says, 'You know, the state of the science now tells me that my conclusions then were either incorrect or exaggerated or misleading,' that is incredibly powerful in any given case," Gabel says.
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