The Los Angeles Police Department has cut in half a backlog of untested DNA evidence from rapes and sexual assaults, according to police figures.

In late 2008, amid increasing pressure from victims' rights groups and elected officials, LAPD officials acknowledged that nearly 7,500 evidence kits collected from rape and sexual-assault victims were languishing in storage freezers, never having been analyzed.

At the time, Mayor Antonio Villaraigosa and LAPD Chief William J. Bratton vowed to address the issue, setting aside funds to help the department outsource the evidence to private laboratories at a faster pace and to bolster the LAPD's own understaffed laboratory. Bratton also announced the formation of a task force of police and outside experts to oversee the effort.

In a letter, Bratton and Deputy Chief Charlie Beck, who heads the task force, updated its members, saying the number of untested evidence kits had fallen to 3,157. At the current pace of testing, the LAPD would erase the backlog by the summer of 2011, Bratton and Beck wrote.

Unexamined evidence kits hold potentially crucial information. Through a complex scientific process, DNA analysts can extract a person's genetic code from the collected samples and compare it to those of known felons stored in state databases.

When a DNA sample collected at a crime scene or from a victim's body is matched to a DNA profile, it can offer prosecutors strong proof of a person's guilt. The evidence also can be used to confirm that someone has not falsely confessed to a crime or to link someone to other unsolved cases.

The LAPD's push to clear the backlog has led to tangible payoffs: Examination of previously untested semen, blood or other genetic evidence matched the profiles of 405 men in the state's databases, the letter said. The department is also on course to hire 26 additional lab staff members by next summer.

In an interview, Beck emphasized that an inventory of the evidence allowed the LAPD to prioritize cases for testing. Evidence from the several hundred cases in which detectives had no known suspects has now been tested, Beck says.

The effort, however, has not been without some setbacks. Plans to build a database to track each evidence kit have been stymied by technical and funding problems, and mandatory furloughs of civilian staff have hampered work at the LAPD's lab, Beck said.

The LAPD's ability to finish the effort is also not assured. In the letter, Bratton and Beck warned that city officials will need to continue to commit funds to keep the testing on track - a tall order as the city tries to navigate through a fiscal crisis that has left a $400-million budget shortfall.