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Exaggerated forensic testimony a key contributor to false convictions


Exaggerated forensic testimony a key contributor to false convictions

On behalf of Patrick T. McNally, Attorney at Law | 
April 29, 2019

Each year, the National Registry of Exonerations sends out an annual report that reveals how many innocent people were exonerated that year, along with information about what problems brought about their wrongful convictions.

Last year, 151 people were found not to have committed the crimes they were convicted of committing. Together, they spent over 1,600 years behind bars. Unfortunately, 2018’s years of imprisonment brought the overall total, calculated since 1989, to over 20,000 years innocent people spent in our prisons before their cases were overturned. And that’s just the innocent people we know about.

Unfortunately, the no. 1 cause of wrongful convictions, according to the Registry, is police and prosecutorial misconduct. In fact, nearly a third of the exonerations came after it was discovered that a Chicago police officer had been framing people on drug charges.

Yet according to a New York Times analysis, another common cause of wrongful convictions is exaggerated testimony by forensic analysts. Even if you assume that these techniques are scientifically valid — which we should not — there are limits to what forensic tests can prove. Yet, far too often, forensic analysts make up statistics like “one in a million” or exaggerate the statistical significance of what they’ve found.

While courts do require forensic analysts to prove they have sufficient training to be considered experts, they apparently don’t hold the analysts to rigorous standards of accuracy about their field of expertise.

“An expert can say whatever they want,” said the director of the registry, who is a professor of criminology, law and society.

“A lot of the problem with forensic testimony is that the diagnosticity is overstated,” said the author of the report and another law professor. Sometimes, it “gets dressed up with this scientific certainty that isn’t justified.”

Consider the example of bite mark comparison. According to the Registry report’s author, bite mark comparison is just a bogus pseudoscience. “It doesn’t even get past the barest suggestion of scientific reality,” she says. Often, it’s impossible to tell if a particular wound is even from a bite.

In the case of Steven Chaney, a comparison of an alleged bite mark to a wax model of Cheney’s mouth seemed to match. The consultant who compared them said there was only a one on a million chance that Cheney had not made the bite. That was enough for a jury to convict him of murdering two people.

In 2018, an appellate judge determined that bite mark evidence had evolved since Cheney’s conviction “in a way that contradicts the scientific evidence relied on by the State at trial.”

Was your case infected with bad forensic science? Discuss your chances for appeal with an experienced criminal appeals attorney.

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