OAKLAND — A man who fatally shot a teenage acquaintance while playing with a handgun two years ago will spend the next 40 years to life in prison, a judge declared Wednesday, agreeing with a prosecutor that the defendant was a career criminal.

Michael Campbell, 21, showed no emotion while he was read his sentence or when family members of Derial Morris Jr. spoke about the pain Campbell caused when he shot the 17-year-old in the forehead.

Campbell, who was 18 when he killed Morris, was found guilty earlier this year of second-degree murder, a crime that usually carries a 25-years-to-life sentence. But Campbell's previous criminal history, which included an auto theft and a robbery, allowed Alameda County Superior Court Judge Leo Dorado to issue a harsher penalty.

"Mr. Campbell has earned his 40 years in state prison," Dorado said.

Campbell shot Morris on April 18, 2007, while he was in an apartment in the Acorn housing project telling a group of people a story while his finger was on the trigger of a gun.