Nine months ago, the San Francisco Police Department Crime Laboratory — a capacious, hangarlike building fronted with palm trees in the old Hunters Point naval shipyard — was rocked by the revelation that a rogue technician, Debbie Madden, had skimmed cocaine evidence from the narcotics unit for personal use. In May, SFPD Chief George Gascón announced the lab's drug section would be closed permanently, and all narcotics testing outsourced.

No one would dispute that Madden's conduct created a major problem for the integrity of drug evidence. Yet as troubling as her actions were, they may have distracted public attention from more consequential shortcomings elsewhere in the crime lab, which continues to operate despite the shuttering of the drug unit. Unlike the Madden affair, which for the most part tainted minor narcotics-possession cases, these mistakes could have significant implications for rapes and murders, and raise questions about the ethical conduct of the district attorney's office in its approach to forensic evidence.

On Dec. 3, SF Weekly reported on its website that a mixup of test tubes containing DNA evidence, reportedly in a homicide case, had been concealed by officials at the crime lab for close to two years. Documents obtained by SF Weekly revealed that records of the 2008 sample switch had been destroyed at the direction of the DNA unit's former supervisor, who — along with the crime lab's then-director — nevertheless denied knowledge of the incident when confronted by investigators from the American Society of Crime Lab Directors (ASCLD), which accredits forensics facilities.

In September, the ASCLD accreditation board issued a report confirming the DNA sample switch. The report also cast doubt on previous statements by SFPD officials about lab security; inspectors found, for instance, that doors to the facility were frequently propped open, exposing highly sensitive DNA evidence to potential contamination or theft.

These issues, on their own, are enough to warrant serious questions about the DNA lab's work. But further information obtained by SF Weekly also indicates that DA Kamala Harris — recently elected California Attorney General — has a troubling history within her own office of covering up problems with genetic evidence used by prosecutors.

In May, defense lawyer Tony Tamburello wrote to Gascón, complaining of alleged unethical conduct by current DNA lab supervisor Cherisse Boland in a murder case. Tamburello asserted that Boland concealed from a grand jury during sworn testimony that the majority of the DNA found on critical evidence did not come from the suspects arrested by police. This omission, in addition to demonstrating incompetence, might "constitute criminal conduct warranting further investigation," he wrote.

The subject of Boland's conduct was taken up by Rockne Harmon, a star prosecutor in the realm of DNA evidence who worked on the O.J. Simpson case. Harmon, who became a consultant at the San Francisco DA's office when he retired after 33 years at the Alameda County DA's office, told SF Weekly that he had submitted a report to the DA's office and SFPD that was critical of Boland's testimony. He recommended this critique be shared with the city's defense bar through a mass disclosure, since it should be available to lawyers seeking to cast doubt on Boland's work in criminal cases. (Harmon declined to discuss his findings in detail, saying that under the terms of his previous contract, the document was the property of the DA's office.)

Yet instead of sharing the information, the DA opted to conceal the problems Harmon had found. Paul Henderson, Harris' chief of administration, went so far as to deny the report's existence in a letter responding to a formal request for the document from SF Weekly under the Sunshine Ordinance.

Harmon says he is concerned that his report has been kept under wraps and came to light only because he chose to talk about it with a reporter. "It wasn't earth-shattering, but it's something that should be out there," he says. "I think what's earth-shattering is what's happened to it."

Such statements from Harmon, whom Harris herself once called "the guru of DNA evidence in the state," are a serious rebuke to the district attorney as she prepares to ascend to statewide office.

The secrecy that until now has surrounded the DNA section's string of mistakes and misconduct allegations is particularly unsettling in the wake of the Madden affair. Following that scandal, Superior Court Judge Anne-Christine Massullo issued a blistering ruling against Harris, finding that her office had failed to fulfill its constitutional obligations under the U.S. Supreme Court case Brady v. Maryland, which requires that prosecutors turn over potentially exculpatory information to criminal defendants.

Problems at the crime lab's drug unit should have been disclosed to defense attorneys, Massullo ruled. The judge also said that the DA's office must proactively seek such information from the police department, rather than relying on the SFPD to turn it over.

The fact that the DA's office has shared neither Harmon's report on Boland nor the ASCLD report on the sample mixup with defense lawyers — who learned of the former and were provided with the latter by SF Weekly — indicates that prosecutors are still failing to comply with this order, critics say.

David Wise, a private defense attorney who specializes in cases involving DNA evidence, said he has filed motions in ongoing criminal cases asking specifically for any new reports on the crime lab, but learned of the ASCLD report's existence only from SF Weekly. "I just can't believe it. I'm shocked," he says. "I'm troubled by the fact that I've asked for exactly this, and [prosecutors have] told me it doesn't exist. I think that's enough for me to be disturbed about, when someone's looking at 25 to life."

Public Defender Jeff Adachi, who also obtained the ASCLD report from SF Weekly, has called for an investigation into whether the erasure of records of the sample switch amounted to criminal destruction of evidence. "Not only did the lab fail to document the switching of samples. They intentionally covered it up," he says. "This is a bombshell." The DA's office's denials about Harmon's report, Adachi adds, are "beyond outrageous. It suggests intentional culpability by somebody" to conceal the document.