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New Crime Lab Protocol Leads to Reviews of "Mixed DNA" Evidence

A new standard, used by crime labs in Texas and nationwide when analyzing multiple sets of DNA taken from evidence, has prompted questions and a review of court cases dating back to 1999.

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This past spring, the FBI notified crime labs there were errors in the data used to calculate the chances that DNA found at a crime scene matched an individual. But it downplayed the impact of the errors on court cases, setting off a low but distinct rumble throughout the criminal justice system nationwide.

After reading the FBI's notice, district attorneys like Galveston County's Jack Roady asked DPS to reassess evidence that had already been tested for use in upcoming trials — this time, using the FBI's corrected data, which was related to population statistics.

"When the FBI sent out the 'pop stat' issue memo, that these were some errors and should not be any issues, I don't have any reason to think they were wrong in that," Roady said.

But a second concern emerged after Roady got his evidence analysis back from one of the eight Texas Department of Public Safety crime labs that tests DNA evidence. Recently, DPS and crime labs nationwide have switched to a more conservative analytical approach when looking at "mixed DNA" — which refers to when more than one individual's DNA is present on evidence.

"It still included the defendant," Roady said of the new analysis this past summer in a case. "However, the likelihood that the defendant was the only source of the DNA went from 1 in a billion, down to less than 1 in a 100."

Luckily for Roady, the evidence tested was not primary or what he called "lynchpin evidence." But the different result was troubling.

"Any change in the evidence causes concern for the prosecutors," he said. "We want to present evidence that we know is reliable."

As word of the new DPS approach spread, so have questions from prosecutors and defense attorneys to the Texas Forensic Science Commission, which spent much of August discussing with its board, attorneys and even the Texas Court of Criminal Appeals as to what it could all mean — most of all, for defendants. 

"While in many cases the changed protocols may have no effect," the commission wrote in an obtuse Aug. 21 memo posted on its website. "But the potential impact on criminal cases raises concerns for both scientists and lawyers."

As the DPS later explained this past week in a memo to attorneys, DNA analysis is a developing science and as standards change, so do the ones used at the state crime labs.

"The Texas DPS Crime Laboratory Service is committed to keeping and remaining current," DPS informed prosecutors in a Sept. 10 memo noting that on Aug. 10, it had switched to a new standard when analyzing "DNA mixtures." 

But the lack of certainty in the new standards, which was not used at all crime labs in the state across the board, has also raised questions. Only eight of the DNA crime labs belong to DPS. Others are operated by local governments. 

"Different labs have used different protocols in Texas, and we don't know the scope of the problem," said Amanda Marzullo, policy director at the Texas Defender Services, a team of lawyers who file appeals for Texas death row inmates. "So someone who could be included in one scenario might not be, in light of these new procedures."

One of the experts who has been working with the forensic science commission to explain to judges and others the interlacing triggers that have prompted questions about DNA analysis is Bruce Budowle of the University of North Texas Health Science Center, who declined to offer a definitive read. 

"I don't have much to discuss as we are still looking into the issue and whether it is a minor or greater problem," Budowle said in an email to The Texas Tribune. "I cannot say until more information is gathered and thus am hesitant to opine at this time."

While the commission's lead as both clearinghouse for concerns and air traffic controller for ideas about how to proceed has won praise from prosecutors, judges and others, the challenge before it has brought to light how science and law in Texas can lead insular lives even when the two intersect.

"DNA is a very hard science," said Rob Kepple, executive director of the Texas County and District Attorney Association. "What we didn't appreciate or know was that after the physical test was done for the mixed samples, there's this level of interpretation that needs to be done."

Although no one is convinced — yet — that the new interpretation standard adopted by DPS and states elsewhere will impact cases, the three-staffer commission's swift action has helped to move government entities in a remarkable collaborative fashion.

On Thursday, in an attempt to determine how far-reaching the new standard could be, DPS sent district attorneys a list of 24,468 lab cases "potentially impacted by this protocol change" since 1999, in which mixed DNA was analyzed. Because one criminal case could involve more than one lab test, the number of defendants and victims included among those lab cases could not be calculated by the Tribune.  

"It's kind of an unknown of the magnitude of what this situation will be," said Skylor Hearn, a former Texas Ranger who is now assistant director over the law enforcement support division at DPS. "We do have an obligation to provide information that has the potential to be exculpatory. As do prosecutors. So we have to give them the information first." 

The new protocol adopted by DPS does not eliminate suspects or victims, insists Hearn. "It's not saying, 'It's not you.' It reduces the ratio, which could impact at trial." 

That reduced ratio, he said could be used to create reasonable doubt. 

In a letter to the district attorneys, Brady W. Mills, DPS deputy director of the crime laboratory service, notified them of next Friday's commission meeting at Dallas' Southwestern Institute of Forensic Science, where DNA experts tapped by the commission will discuss how to proceed.

It is expected to draw a large crowd, from DPS staff and prosecutors to judges and defense attorneys. One stakeholder joked that perhaps AT&T Stadium, home to the Dallas Cowboys, might be the right venue to accommodate all of those who are interested in attending.

Until then, Texas prosecutors are busy combing through DPS' 24,468 lab test list see whether there was a resulting criminal case occurred and whether they need to have the DNA data submitted for another analysis under the crime labs' new standard. 

Bell County District Attorney Henry Garza has already set up a review of the DPS lab cases which involve 100 criminal cases in that county since 1999. 

"It's a serious matter and entails a lot of work," Garza said.

In Galveston County, Roady has notified both his Commissioners Court and judges that any case that is re-examined will require notification to defendants and their attorneys.

That notification to defendants is expected to be costly, and no one has a handle on exactly how it will be done uniformly and how it will affect local budgets. For now, those in the criminal justice community are waiting until there are more answers next Friday. 

"We very recently became aware of this issue and have notified defense attorneys on all pending criminal cases where there is DNA testing," said Cynthia Meyer, spokeswoman for Texas Attorney General Ken Paxton. "We will be monitoring this meeting and any recommendations from the Forensic Science Commission to address this issue."


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Courts Criminal justice State government Death penalty Department of Public Safety Judiciary of Texas State agencies Texas Court Of Criminal Appeals