Woo said in the e-mail that she spoke to the lab's director several times about Madden, who was apparently unhappy with the lab and strategically picked times to call in sick, creating a backlog in the already short-staffed lab.
"The situation at the crime lab is becoming ridiculous," Woo told Chief Assistant District Attorney Russ Giuntini in the e-mail. "Please try and get SFPD's attention concerning this issue."
The e-mail was among more than 1,000 pages of documents made public by prosecutors after a judge ordered Tuesday that they be turned over to defense attorneys handling drug cases that may be affected by the emerging crime lab scandal.
Madden, 60, admitted to police during a Feb. 26 interview that she used cocaine found at work to mask a drinking problem. She took a leave of absence in December after an audit discovered cocaine was missing from the lab, and retired last month after 29 years.
The investigation is ongoing, and Madden has not been charged. Her attorney, Paul DeMeester, said Wednesday that Madden's February talk with police was forthright.
"She was very honest and talked about all of the wrongdoing she had committed at the lab, which is very minimal," DeMeester said.
The lab's drug analysis unit is closed indefinitely. So far, prosecutors have dismissed more than 365 drug cases and have been unable to charge an additional 450 due to the lab's closure.
Public Defender Jeff Adachi said Woo's e-mail is a "burning red flag" about the crime lab's problems and Madden herself. He has called for an independent investigation of the lab.
"This information is more than explosive," Adachi said. "It is the TNT that should've ignited an investigation months ago, but instead it was ignored by people high up in the district attorney's office who allowed Madden's credibility to remain unchallenged."
A spokesman from the district attorney's office did not return messages seeking comment.
Woo's e-mail is apparently the first indication prosecutors were aware of potential problems with Madden before police suspected her of skimming cocaine evidence used for testing.
Woo said in her e-mail that Madden was "becoming increasingly UNDEPENDABLE for testimony."
She said Madden failed to show up in court to testify two days after calling in sick, despite being told prosecutors needed her. She said Madden's supervisor offered to have a car pick her up to testify and return her home, but Madden refused.
"I was told that when she called in sick, her supervisor asked if she could send someone to do a wellness check. Her request was denied," Woo wrote.
In a Nov. 24 memo to Assistant Police Chief Kevin Cashman, Giuntini brought up the lab's short-staffing but made no mention of Madden's behavior.
Assistant Police Chief Jeff Godown, who was put in charge of the lab last month, said Wednesday he was unaware of any notification police received about Madden and the lab based on Woo's e-mail.
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"I have nothing that shows they notified us," Godown said. "My question is, 'Who within the SFPD was notified about the memo?' We're trying to find that out."