Police Chief Bill Scott. Screenshot.

The San Francisco Police Commission grilled police department leaders Wednesday about the policies and procedures that allowed officers to use DNA collected from a rape kit to link a sexual assault victim to an unrelated case.

“This was a horrendous mistake,” Police Chief William Scott. “It’s been corrected. Policies have been put in place for this to not happen again.”

Last month, District Attorney Chesa Boudin revealed his office had dropped its case against the woman, after learning how police had used her DNA. Boudin said the practice could violate victims’ constitutional rights and deter people from cooperating with law enforcement and prosecutors.

On Wednesday, Scott promised commissioners that his department will not use DNA samples collected from rape victims to investigate them for unrelated crimes.

The police chief said his department has been flooded with questions from advocates for rape victims asking, “Will my DNA be used to investigate me for crimes outside of my sexual assault?” 

“The answer is ‘no,’” Scott said.

Separate DNA databases

Acting Crime Lab Director Mark Powell explained to commissioners that the police department works with two separate DNA databases, a quality assurance database and the Combined DNA Index System Database (CODIS), which the FBI uses to track convicted felons. 

The department’s quality assurance database includes thousands of samples, including those from rape kits, crime scenes, crime lab technicians and lab visitors. Powell said the lab uses the database to check samples for contamination.

The lab does not upload DNA samples from sexual assault victims to CODIS, Powell said.

But when the lab ran a DNA sample collected from the scene of the property crime through both CODIS and the quality assurance database, it uncovered a match with a rape victim. 

“There was a piece of the evidence that was gathered from the scene and it was run through the system, and she appeared in both the quality assurance database from her sexual assault kit, as well as the CODIS database from her prior arrests,” Police Capt. Sean Perdomo of the Investigations Bureau told commissioners Wednesday.

Commissioners said the department’s practices raised ethical concerns. 

“Are you notifying victims that their DNA is being used for other purposes?” Commissioner Cindy Elias asked.

“Are we notifying victims of survivors any time their DNA is run against quality assurance for contamination purposes? The answer is ‘no,’” Scott said. He said he doubts other DNA samples from sexual assault survivors have been used to check for unrelated crimes.

Retaining samples 

Scott has acknowledged that, for seven years, the department’s crime lab has entered DNA samples collected from victims of violent crime, including children and sexual assault survivors, into the quality assurance database.

Commissioners asked why the lab has kept DNA samples in its database for years. Powell said it was common practice to retain samples for long periods of time. “It wasn’t atypical to have something take years to come into the lab,” he said.

Scott said the department is considering destroying quality assurance DNA samples after 60 days.

Scott told the commision that the department is conducting an investigation into its use of DNA evidence. Officer Peromo said that, so far, the department has identified DNA from 11 rape kits that matched another sample. Officers are investigating whether such matches were used to charge any victims.

Commissioner Ellis suggested that another oversight body, such as the City Attorney’s office, should conduct a separate investigation. Scott said that wasn’t off the table, but he would provide the commission with updates on the department’s investigation.

“We’re going to be transparent with you, with whatever we come up with,” Scott said.


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REPORTER. Annika Hom is our inequality reporter through our partnership with Report for America. Annika was born and raised in the Bay Area. She previously interned at SF Weekly and the Boston Globe where she focused on local news and immigration. She is a proud Chinese and Filipina American. She has a twin brother that (contrary to soap opera tropes) is not evil.

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  1. So they ran her DNA through the wrong database. What use is that information to the case, none at all. Victim info should be more protected out of respect, but not a reason to drop a case.

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  2. It seems we are glossing over or ignoring that fact that she had a DNA hit in CODIS (the criminal database) as well as the ancillary QA database. While I agree with everything said about the QA database, it feels like a “look over here” moment from Boudin’s office. Considering the timing this press conference initially happened was when Scott and Boudin were going tit for tat about the Investigation MOU.

    If this was sole source from the QA database, then sure, that should be an even bigger issue. What the article says is that CODIS matched, and then the QA matched, so the tech included both results.

    Looks bad on paper, yes. Absent the quality assurance hit, you still hav the CODIS hit.

    Boudin is under public pressure. So is Scott. It makes sense that each would try to sling mud on the other.

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    1. I came away with the same impression. So the unanswered question in this case is: How was the decision made to identify this woman as a suspect? It may be impossible to prove a investigator who had knowledge of the QA database result didn’t use it to establish probable cause.

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    2. Yes, ironically it looks like under Boudin, the fact that they found a match in the rape kit DNA actually *helped* the woman avoid charges in this case, s her DNA was also matched in the criminal database from previous arrests .

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  3. > The department’s quality assurance database includes thousands of samples, including those from rape kits, crime scenes,

    > Scott has acknowledged that for seven years, the department’s crime lab has entered DNA samples collected from victims of violent crime, including children and sexual assault survivors into the quality assurance database.

    In truth SFPD and probably most police departments are maintaining DNA on a vast number of people whose DNA they encountered at a scene who have never been suspects in a crime, never been charged for a crime

    All of that should stop.

    Sometime after an investigation is closed, all the incidental DNA collected should be purged from the databases

    For great laughs, why don’t you ask Commissioner Hamasaki about his thoughts on this?

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