Biological Crime Evidence May Be Missing

Biological evidence in thousands of sexual-assault cases in Los Angeles County may have been lost or destroyed by law enforcement over the past six years, according to the district attorney’s forensic science director.

Deputy Dist. Atty. Lisa Kahn said Tuesday she believes that based on state crime statistics and the average clearance rate for sex offenses, there could be as many as 3,000 to 4,000 unsolved cases for which there is no evidence now being stored by the Los Angeles Police Department or county Sheriff’s Department.

Kahn said that in applying about two years ago for state funds to perform DNA tests on cold cases, the LAPD and Sheriff’s Department reported they had preserved the biological evidence for about 2,000 unsolved rapes and slayings involving sexual offenses. Kahn estimates the agencies should have had evidence for about 6,000 cases.

“The real tragedy is that we will not be able to solve these cases, and the violent perpetrators of these crimes are still out there,” she said.

Her comments brought strong denials from authorities who are in charge of the property and evidence rooms for both agencies.

Kahn’s estimates “sound way out of whack to me,” said David Peterson, commanding officer for the LAPD’s property and evidence unit. “I just don’t see that happening here.”

He and Peter Zavalo, head of the sheriff’s evidence unit, said destruction of evidence in most cases can only be authorized by investigating officers. They say detectives do not issue such approvals unless the statute of limitations on the offenses have expired or the cases have been tried and all appeals completed.

While conceding that her estimates are “soft” because they are based on extrapolations using statewide statistics from the Department of Justice, Kahn said, “I believe beyond a reasonable doubt” they are close.

Kahn says it is important for law enforcement agencies to be diligent in keeping biological evidence in old cases because major legal and forensic developments in recent years have given the material increased importance.

For instance, the statute of limitations for sex offenses has increased in recent years, and a national database of DNA evidence obtained from prisoners has been expanding exponentially. The more names in the database, the more likely law enforcement can solve cold cases, Kahn said.

But she said the cases cannot be solved if agencies destroy rape kits, semen or blood traces or other biological evidence.

In rejecting Kahn’s figures, Peterson said her method for estimating the amount of missing evidence is “highly dubious” and that evidence is not destroyed due to lack of storage space.