While district attorney for San Francisco, Kamala Harris withheld evidence that could have exonerated defendants on multiple occasions, in violation of a key due process ruling by the Supreme Court.

Between 2004 and 2010, Harris’s office failed to inform defense attorneys about criminal and professional misconduct records that raised questions about the credibility of government witnesses. The lapses led to the dismissal of nearly 1,000 cases and a scathing 2010 ruling by a Superior Court judge that accused Harris’ office of breaching due process rights.

Legal scholars told the Washington Examiner that Harris’ office appeared to have violated the Supreme Court’s 1963 Brady v. Maryland decision. The ruling held that prosecutors must turn over potentially exculpatory evidence to the defense.

There is a “clear causal link between Brady violations and wrongful conviction” said Craig Trainor, a New York attorney who specializes in due process cases.

“The reasons for failure to disclose exculpatory evidence range from bad faith to inexperience to excessive caseloads to a tunnel vision to get the ‘guilty defendant’ at all costs to rank politics, as we see in Kamala Harris’ case,” he said.

Jason Kreag, a law professor at the University of Arizona and a former staffer at the Innocence Project, said Brady is also crucial because it “is designed to promote fairness in our system.”

Kreag said this was particularly true in Harris’ case. “There is no doubt that the prosecutor’s case is impeached when it is built on information from people who have credibility problems, as was the case here. When that happens, prosecutors owe a duty to disclose to the defense things that can be used to impeach the state’s case. That was a failure here.”

He said prosecutors can face disciplinary action or disbarment for Brady violations, but such repercussions are rare.

In December 2009, Deborah Madden, a long-time technician at the San Francisco Police Department crime lab who often testified as a trial witness for the district attorney’s office, was accused of stealing cocaine from the unit. This was not her first brush with the law, according to court records. Madden had been arrested for a domestic violence incident at her home in 2007. She was charged with assault with a deadly weapon and later found guilty of misdemeanor domestic violence charges.

The police department opened its own disciplinary proceedings for Madden after the arrest. Police officials also realized her record might have to be disclosed to defendants: Her official file included a Post-it labeled “Brady Implications.”

Top officials in Harris’ office were aware of other problems with Madden. On Nov. 19, 2009, an assistant district attorney emailed Harris’ deputy Russ Giuntini and informed him that Madden seemed to be trying to sabotage the work of the crime lab.

Madden was “increasingly UNDEPENDABLE for testimony,” said the email. “The problem with Deborah Madden does not appear to be isolated … anecdotally I am told Debbie is unhappy and strategically picks days and times to be sick which have the greatest impact on lab work.”

After Madden’s drug theft went public, dozens of defendants sought to have their convictions vacated, arguing that the police and district attorney violated their due process rights by withholding material information about Madden.

San Francisco Superior Court Judge Anne-Christine Massullo appeared to agree. In a April 2010 ruling, she said Harris’ office violated Brady policy.

“The District Attorney failed to disclose information that clearly should have been disclosed,” wrote Massullo.

When the judge asked the district attorney’s office for its policy on handling Brady disclosures, she was told the DA had no such system in place.

“Failure to implement any type of procedure is a violation of [Supreme Court rulings] and California’s statutory discovery obligations in criminal cases,” wrote the judge.

The controversy unearthed other cases where Harris’ office had withheld important information on government witnesses. The San Francisco Chronicle reported that Harris’ office had compiled a list of over 100 law enforcement officials with criminal or misconduct issues but objected to sharing this information with defense attorneys without a court order.

One toxicologist who worked on drunk driving cases, Ann-Marie Gordon, had been rebuked by a Washington state court for engaging in professional “fraud” while working at a local crime lab in 2007, according to the Chronicle. Gordon started working in San Francisco in 2007. Harris’s office did not disclose her background to defense attorneys until the spring of 2010.

Harris’ office was informed of other inadequacies at the police crime lab that it declined to make public. In 2007, Harris hired veteran forensics expert Rockne Harmon as a DNA consultant, paying him $140,000, according to a copy of the contract. As part of his work, Harmon wrote a lengthy memo to top officials in the district attorney’s office that raised concerns about the reliability of the crime lab’s DNA testing unit in April 2010, according to San Francisco Weekly.

After the Madden scandal broke, Harris insisted she never saw the memo. Her office also declined to make the document public. Harmon called for the DA to release the memo, saying it was important to understand the scope of the problems at the crime lab.

“I’m not pleased that the full story — the full, true story — is still not out there,” Harmon said. “It’s just something I’m not used to seeing as a prosecutor.” The memo has still not been released, despite efforts from defense attorneys to subpoena the document.

Harris’ campaign did not respond to a request for comment.