by Matt Clarke
The mission of the Texas Forensic Science Commission (TFSC) is to set standards for the use of scientific evidence in the state’s criminal justice system. In investigating the proper standards for DNA testing during the summer of 2015, the Commission came to the unsettling conclusion that the population distribution statistics used to calculate the probability of one person having the same DNA profile as another were off. Way off.
Using a protocol that had been in place since 1999, DNA experts routinely testified that the probability of a random person’s DNA matching the DNA profile discovered at a crime scene was one in millions or even billions. However, in May 2015 the FBI announced there were discrepancies in the population statistics used to calculate DNA probabilities in cases involving genetic material from multiple people, and the Commission issued a new protocol based on the FBI’s updated data.
When the new protocol was introduced, forensic scientists believed it would simply be a refinement of the numbers produced by the old method. That’s what defense attorney Roberto Torres thought after old protocol calculations indicated the likelihood of crime scene DNA that was similar to his client’s being somebody else’s was less than one in a million.
“When they retested it, the likelihood that it could be someone else was, I think, one in 30-something, one in 40. So it was a significant probability that it could be someone else,” Torres stated.
“We have to go back and identify which of those cases involved DNA mixtures where the lab may have given incorrect results,” said Galveston County District Attorney Jack Roady. “It’s going to be a Herculean task, but we’re gonna do it.”
Experts have coined the term “CSI effect,” in which juries, and even prosecutors and defense attorneys, believe that science provides a definitive answer as to whether a defendant committed a crime or not. DNA is the gold standard of forensic evidence, and many people put a great deal of faith in DNA test results.
“And it’s not faith they should have had to begin with,” observed Keith Inman, professor of forensic science at California State University, East Bay.
Inman, who has studied DNA evidence since the 1980s, said Texas labs simply got ahead of themselves in analyzing the results from cutting-edge testing kits that could extract tiny amounts of DNA from crime scenes. The mistake was using math that was developed for DNA samples from medical labs, not the “weak,” mixed and often contaminated samples typically recovered in criminal cases.
PLN previously reported the misapplication of statistics used to determine the probability of a random DNA match from a database. Those errors also resulted in millions-to-one odds being reduced to much lower statistics for DNA matches. [See: PLN, Jan. 2009, p.24].
NYU law professor Erin Murphy, who authored a book titled Inside the Cell: the Dark Side of Forensic DNA, said people fail to understand that DNA analysis can be subjective.
“[Juries] are even willing to go a step further and say, ‘We’ll convict on the basis of DNA, even in the face of evidence – non-DNA evidence – that it isn’t the perpetrator,” Murphy noted, pointing out that other forensic sciences such as bite mark analysis and hair analysis had been accepted for years but were now discredited.
“I feel like we’re clinging to a life raft and saying, ‘Well this one will save us!’ But I think that both wrongly inflates DNA’s capabilities and it also is just overlooking the part of the story of these old techniques, where they were used in our system for decades without challenge,” he added.
By January 2016, the Texas Forensic Science Commission, county prosecutors and crime labs across the state had begun an effort to identify both pending and past cases affected by the older DNA protocol issues. In Harris County alone – home to Texas’ largest city, Houston – prosecutors identified approximately 24,000 cases involving DNA evidence that needed to be reviewed.
As part of this effort, the Texas District and County Attorneys Association recommended that prosecutors contact potentially affected defendants and inform them about evidence retesting procedures.
In Travis County, the Austin Police Department suspended operations at its crime lab in June 2016, in order to allow for the hiring of a new administrator, acquisition of new equipment and training in updated federally-recommended DNA testing protocols.
The Austin crime lab suspension came at a cost – pending requests for DNA analysis reached a backlog of approximately 1,300 cases at the time of the suspension, in addition to 1,297 cases already identified by Travis County prosecutors as needing reviews of DNA profile statistics.
Notably, the American Society of Crime Laboratory Directors Lab Accreditation Board continued to give the Austin lab passing audit scores even though it was using the older DNA testing methods.
“One would think it would have been picked up,” stated Lynn Garcia, the TFSC’s general counsel. “It raises questions about what the auditors were doing.”
Despite the fact that the FBI’s advisory regarding the need to update DNA statistical protocols applied to crime labs nationwide, Texas appears to be one of very few jurisdictions that has taken such reforms seriously.
In a statement made to the Dallas Morning News in January 2016, Barry Scheck, director of the Innocence Project, reported the findings of an informal poll he had conducted among forensic scientists from around the nation. “Texas is the only place that’s systematically trying to correct” the problem with DNA probability statistics identified by the FBI, he said.
In December 2016, the Texas Department of Public Safety decided to retain only two of the six DNA analysts employed at the Austin crime lab, citing “significant challenges that impact confidence in the work product” of the lab’s DNA testing. The crime lab is expected to remain closed for over two years, and improvements will cost up to $14 million.
Sources: www.wfaa.com, www.npr.org, www.click2houston.com, www.mystatesman.com, www.dallasnews.com
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