An investigation soon revealed that small amounts of cocaine were missing, and the scandal has just snowballed from there.
Hundreds of narcotics cases may have to be thrown out, the drug-testing lab has been closed indefinitely, and outside reviews have unmasked even deeper concerns with how evidence is handled at the facility. The scandal has served as an embarrassment to the police department and raised questions about why officials weren't more proactive in dealing with the problems.
"Anybody who doesn't see the magnitude of this problem is either blind or stupid," San Francisco Police Chief George Gascon said after a review cited bad management at the lab has led to poor practices.
The district attorney's office has already thrown out or not charged 550 cases because of possible evidence tampering, and is reviewing about 1,400 more for possible dismissal.
A final decision hasn't been made on how many ultimately will be tossed, but may come Friday. Authorities are trying to salvage some cases by having drugs retested at other labs; they also may refile some of the dropped cases.
The woman accused of skimming drugs from the lab for her own use, Deborah Madden, has not been charged. Madden took a leave of absence from the lab in December following an audit that found cocaine was missing from the lab, then retired last month. She was a criminalist for 29 years.
Madden, 60, was convicted of misdemeanor domestic assault in 2008 - a conviction not disclosed to the proper authorities until the drug scandal surfaced. Gascon has said it was a mistake the conviction wasn't disclosed.
During a recent search of her home, police discovered small amounts of a "white powdery substance" believed to be cocaine.
Her lawyer, Paul DeMeester, last month sought to downplay the allegations and compared the situation to a bartender who sneaks a drink from a brewery. He said the larger issue is the problems at the lab.
"What's clear is that there's a systemic failing with the San Francisco crime lab that is completely separate and apart that has nothing to do with my client," he said.
DeMeester said Friday that he and Madden are "just waiting to see what happens" once authorities complete their investigation. "If they bring charges, we'll deal with it."
An audit requested by Gascon revealed that employees at the lab were overworked and not doing their jobs properly.
The lab had at least three technicians working there between July and December, each handling about 5,000 to 7,000 cases a year. The state's average is slightly more than 1,000 cases per year, the report said.
Gascon said the department will hire at least six more technicians to decrease the workload.
The report also found that technicians often left drug evidence in unsecured boxes or lockers ripe for possible theft, and technicians did not record when they may have reopened evidence sampling. The lab also failed to calibrate scales used for weighing drugs, the report said. In a criminal case, the weight of the drug can result in a greater or lesser sentence.