BRIDGEVIEW, Ill. (AP) -- A judge has cut two years from the prison sentence of a former Chicago police officer involved in an auto accident last year that killed two teenagers.

Cook County Judge David P. Sterba granted Jason Casper's request for a shorter sentence Thursday, urging Casper to keep his word about wanting to share his experience with others.

"You will always owe that to Mohammed and Ahmad, and it's a debt that can never be fully repaid," Sterba said, referring to the two teens who died.

In asking for the sentence reduction two weeks ago, Casper had said he wanted to spend time helping others.

"I strive to give my life in prison a purpose so that the lives of those two boys weren't lost in vain," he said.

Casper, 25, had been sentenced to 12 years in prison in January for aggravated driving under the influence and one five-year term for aggravated battery, to be served concurrently.

Casper's blood-alcohol level was more than twice the state's legal limit when he ran a red light in Tinley Park and caused a three-car accident on Feb. 12, 2005, authorities said. He was off-duty at the time.

Both Ahmad Shaban, 16, of Orland Park, and Mohammed Shuaibi, 17, of Tinley Park, were killed in the crash.

Casper was fired from the police department last June.