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SFPD crime lab's DNA evidence could be tainted by concealed mistakes 

Wednesday, Dec 15 2010
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Scientific and ethical lapses at the lab, and the failure to disclose those problems to defendants, could force prosecutors to re-evaluate and perhaps dismiss cases that depend on DNA evidence from recent years, even those that have already resulted in convictions. A similar phenomenon was seen in the wake of the Madden scandal, when hundreds of drug cases were dropped.

When it comes to the DNA lab, a high volume of dismissals is unlikely. SFPD analysts handle 450 cases a year, less than one-thirtieth the caseload of the narcotics unit before it was closed. But much of the DNA lab's work, unlike that of the drug section, involves serious violent crimes.

The tainting or reversal of even a handful of prosecutions and convictions in those cases could have deep reverberations in the city's criminal-justice system. Last week, motions to dismiss two rape cases had already been filed by defense lawyers claiming that the DA's failure to disclose problems at the DNA lab amounted to a violation of their clients' constitutional rights. Adachi says his office plans to ask for more dismissals in the coming weeks based on the same argument.


Recent news coverage of the DNA section of San Francisco's crime lab has focused on problems less ethical or scientific than logistical — principally the enormous backlog in testing of evidence. That isn't to say such delays can't have serious consequences. Earlier this year, several news organizations reported on the case of Donzell Francis, a convicted rapist and suspected murderer who allegedly continued on a spree of violent crimes while his DNA, collected from the body of a slain transgender prostitute, sat untested for two years.

Still, case-processing bottlenecks of this kind, and the attendant cries for bigger budgets and more staff, are common to most branches of law enforcement. Clues that something more fundamental was wrong at the DNA lab surfaced in November 2008. That's when Bicka Barlow, an attorney and former geneticist who serves as the public defender's office in-house expert on DNA evidence, received an anonymous letter detailing two significant problems in the crime lab's DNA division.

"The laboratory is continually kept in an unsecured manner," the letter stated. "If you go out to the crime lab in the afternoon, the front door to the building and the doors to the laboratory are propped open, which allows anyone access to the facility."

Additionally, the letter writer alleged, "There was a recent homicide case that was a rush in the laboratory as the case was going [to] trial. During the analysis there was a sample switch. At the direction of DNA Supervisor Matt Gabriel, the sample switch was covered up by relabeling the tubes containing the DNA evidence and by manipulating the LIMS system in order to hide the sample switch." (LIMS, which stands for Lab Information Management System, is generic shorthand for the computer databases in which forensics analysts' work records are stored.)

At the time, Barlow says, she wasn't sure what to make of the letter. After some thought, she got in touch with a federal prosecutor she knew, who in turn dispatched an FBI agent to collect it. She never heard from the Bureau on the subject after that. Officials at the San Francisco field office of the FBI did not return calls as to whether a federal investigation is being conducted into the crime lab.

Barlow was already uneasy about the lab's work. The small crew of analysts handling evidence in rape and murder cases was somewhat young and inexperienced. Section head Gabriel was an enigmatic figure who seemed to relish the adversarial back-and-forth of courtroom proceedings. (Barlow says he once broke into laughter after a judge sustained an objection to her questioning.)

Under Gabriel's leadership, Barlow believed, the SFPD's DNA analysts had come to see themselves as an arm of the district attorney's office in criminal prosecutions, rather than as unbiased scientists. "They're so interested in doing a test and getting a result that they'd rather have poor data than no data," she says.

While the first letter about the DNA sample switch led nowhere, the whistleblower behind it was persistent. In July 2009, he or she sent another, more detailed communication to ASCLD's accreditation board, repeating the allegation of the sample switch and its subsequent concealment through alteration of the lab's official records, this time identifying the rookie analyst who made the mistake as Tahnee Nelson. (The letter stated that the switch happened in the first case Nelson worked on.)

The whistleblower also repeated the allegation about easy access to the DNA lab, and in doing so revealed his or her identity as an employee there: "On at least two occasions I was working ... and was approached from behind by individuals that were able to make their way into the laboratory unescorted."

ASCLD, in accordance with its policies, gave the letter to the SFPD and asked for a response. In a letter dated Aug. 28, 2009, then-crime lab manager Jim Mudge denied any knowledge within the lab of the alleged problems. Regarding the sample switch, he wrote, "I have informed Matthew Gabriel, DNA Technical Leader, of this allegation and reviewed with him the DNA Unit Corrective Action Log. There were no instances of corrective action for Ms. Tahnee Nelson ... from the last quarter of 2008." Mudge further wrote that the lab's quality assurance manager "has indicated to me that she is not in possession of specific casework information as the allegation claims."

Mudge's language was oddly couched. The central accusation of the whistleblower letter was that records of the sample switch were destroyed, yet the lab director responded by saying no records of such an event existed.

On the subject of security, Mudge was less ambiguous. "It is the laboratory's policy to maintain a secure environment and keep doors shut at all times," he wrote. "On occasion doors may need to be propped open for a brief period of time while transactions of large items of evidence or lab equipment are moved through the Laboratory. It is my responsibility to insure [sic] this only occurs when necessary." He added, "Any unescorted individuals who may gain access to the Laboratory work spaces, as the allegation claims, would have been sworn SFPD members seeking lab staff for a case-specific purpose."

About The Author

Peter Jamison

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