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.

Prosecutor Rockne Harmon, pictured during the O.J. Simpson trial, says he is troubled that DA Kamala Harris concealed his report criticizing the DNA lab’s supervisor.
AFP/Getty Images
Prosecutor Rockne Harmon, pictured during the O.J. Simpson trial, says he is troubled that DA Kamala Harris concealed his report criticizing the DNA lab’s supervisor.
Deputy Public Defender Bicka Barlow first heard of a DNA sample mixup in a homicide case through a whistleblower letter.
JP Dobrin
Deputy Public Defender Bicka Barlow first heard of a DNA sample mixup in a homicide case through a whistleblower letter.

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."

Mudge's protestations might have sufficed, were it not for the confluence of two factors: the Madden scandal and the lab's need for reaccreditation. In August 2010, the lab was due to renew its accreditation for an additional five years. In light of the media feeding frenzy around Madden, the board figured it had better take another look at the crime lab's operations, and ASCLD inspectors paid a visit to San Francisco.


ASCLD, based in North Carolina, is not known for being an exacting watchdog. It is actually an umbrella group that encompasses a trade organization and a for-profit consulting group that helps member labs pass inspections, and its accreditation process is entirely voluntary.

The accreditation division is headed by Ralph Keaton, a former agent at the now-disgraced North Carolina State Bureau of Investigation, where a state attorney general's investigation recently uncovered 200 cases where lab analysts tainted or misrepresented forensic evidence. Amy Driver, a former Los Angeles Police Department forensic scientist who runs an industry blog, BulletPath, describes ASCLD as a "good ol' boy system."

Nevertheless, investigators reported troubling findings in their September report on San Francisco's crime lab, which was first released by the SFPD in response to inquiries from SF Weekly. Foremost among them were dual confirmations of the whistleblower's allegations that records of a sample switch had been destroyed and that lab security had been inadequate.

Despite Mudge's previous assurances that lab security was airtight, accreditation board investigators found that quality manager Marty Blake "readily admitted" that "the lab had problems with the biometric fingerprint access system working correctly" prior to November 2009, when a new card-access system was installed. "At times before the proximity card system was installed she observed that doors to the building and laboratory secure areas were propped open," the report noted.

And the DNA mixup? "Interviews with laboratory staff verified that the sample mixup did occur," the report stated. Investigators found that the last tube in a batch of testing samples, which should have been clear — what analysts call an "extraction negative" — was found to be colored. With Gabriel's approval, Nelson switched the labels on that tube and an adjacent clear tube, believing they were the only two that had been out of place. According to the report, "The DNA typing results were reviewed by the supervisor and the case showed no discrepancies in the DNA typing results, no further corrective actions were taken by the laboratory."

This in itself was an extremely sloppy way to fix the problem, according to Jim Norris, a Redwood City–based forensics consultant who headed the SFPD Forensic Services Division for nine years before retiring in 2004. A misplaced tube in a sample batch could potentially indicate that all of the DNA evidence during that round of testing is out of place and mislabeled, he said, and requires that testing be performed from scratch to ensure accurate results.

"You can say, 'I know how the mistake was made, and I know which two tubes are which,'" he says. "But are you really sure? The correct thing to do there is go back and start over."

An equally if not more serious breach of lab protocols stemmed from the lack of records. While some record of the switch may have remained in the lab's computer system, the inspectors noted that "no documentation of the incident" could be found in the case files, where they could be viewed by prosecutors or defense attorneys. Oddly enough, the report stated that this destruction of records was carried out "according to the DNA Unit standard practice," leading to a finding of "noncompliance with [ASCLD's] requirement to maintain examination documentation."

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