TREMENDOUS advances in the use of DNA evidence as a crime-solving tool have increased public safety over the past two decades by taking serial rapists and murderers off the streets. The most recent example was the arrest and charging of the man suspected of killing at least 10 people in South Los Angeles, dubbed the "Grim Sleeper."

To fully grasp the extent of these achievements requires an examination of the relatively brief history of the use of "genetic fingerprinting" in the criminal justice system.

DNA evidence was first used in 1986 in Leicester, England, when detectives were unable to identify a suspect in the savage rape and murder of two girls. Police took blood samples from more than 4,500 males and compared them to biological evidence recovered from the crime scene. Based on this novel scientific technique, a popular 27-year-old baker was arrested and convicted of those crimes.

In 1989, then-Attorney General John Van de Kamp declared that DNA "was ready to go to court."

In the first criminal case in California, a Ventura County judge found DNA evidence to be compelling and convicted the defendant, Lynda Axell, of murder in a bench trial.

About the same time, Los Angeles County prosecutors were poised to introduce DNA evidence in the courtroom. After months of legal and scientific wrangling over the admissibility of this new scientific evidence, a judge ruled that DNA evidence had widespread acceptance by the scientific community and could be used at trial. That evidence was presented to a jury and, in March 1990, Henry Wilds was convicted of multiple rapes.

Over the next decade, DNA was increasingly used in criminal investigations and prosecutions.

In 1998, the state Legislature enacted Penal Code Section 296, establishing the first statewide database of DNA samples. Though limited to collections from those convicted of specific violent felonies, it marked another major achievement.

With the increased reliance on DNA evidence to solve cold cases and put away killers, Bruce Harrington launched a statewide campaign in support of Proposition 69, The DNA Fingerprint, Unsolved Crime and Innocence Protection Act.

Harrington hoped the creation of an all-felon database would increase the chances that he and other family members of murder victims and rape survivors might some day get justice.

In my ballot argument in favor of Proposition 69, I stated that the new law would dramatically increase the chances of solving crimes, stopping serial killers and rapists, and freeing those wrongly accused of crimes.

In November 2004, California voters overwhelmingly approved Proposition 69.

The latest advance in the use of DNA evidence in criminal cases occurred in the spring of 2007, when at my urging, Attorney General Edmund G. "Jerry" Brown Jr. began to re-examine his agency's ban on the use of partial matches to solve crimes.

A partial match is a powerful tool that can be used when the match between DNA recovered at a crime scene is close - but not a perfect match - to an offender in the database.

Another technique called familial searching can be used to determine if the source of that profile is a relative of the offender.

With my strong support and encouragement, Brown in September 2007 announced that he would approve familial searches in California. Our state joined Colorado as one of just two states that approved familial searching.

California's carefully worded and thoughtful familial search policy and protocols articulate the necessity of striking a balance between privacy concerns and the need to provide information that may solve violent crimes.

On July 7, 2010, after years of heartbreaking disappointment, the power of the familial searching technique was realized on a worldwide stage. Lonnie David Franklin Jr., 57, was arrested and charged with 10 murders that had occurred during a killing spree that began in 1985.

This is the nation's first successful use of familial matching in a major case.

We now know that familial DNA searches provide a powerful scientific tool for solving serious crimes. Our challenge is to expand and improve DNA technology and its uses in the criminal justice system.