Attorney General Jerry Brown stood outside the courthouse and told reporters the collection of DNA is no different than taking a suspect's fingerprints when he's booked into jail.
"I see it as a fundamental protection for the people of California. DNA is the fingerprint of the 21st century," he said.
In California, 1.5 million DNA samples have been collected from felony suspects since the voter-passed law went into effect in January of 2009.
Brown says so far, the database has led to the identification of suspects in more than 970 rapes, murders and other serious crimes.
"This is a very important technology. It holds great promise of saving lives," he said.
Mark Sconce's 12-year-old daughter's killer was positively identified from the database. He says DNA protects the innocent, as well as convicting the guilty.
"Well when they found my daughter, myself, all of my brothers, my father, my 16-year-old son, we all had to give. They asked us to give DNA samples and I had no problem with that. I have not done anything wrong in my life," Sconce said.
But an attorney for the American Civil Liberties Union argued taking DNA violates the Fourth Amendment protection from unreasonable search of people who haven't been convicted of a crime.
'"What's wrong is invading the physical privacy, the bodily integrity and the genetic privacy of tens of thousands of innocent Californians who are arrested every year because a single officer believes that they might've committed a felony when those people are never, ever convicted of anything -- not a felony, not misdemeanor, not an infraction. They are innocent," ACLU attorney Michael Risher said.
The three-judge panel that heard the arguments could take several months to reach a decision and ultimately both sides believe this case will be decided in the U.S. Supreme Court at the 9th Circuit Court of Appeals.
Meg Whitman, who's running against Brown for governor, also supports criminal DNA sampling. It may be one of the few things they agree on.