OAKLAND -- Almost a year after Jose Lumbreras killed his girlfriend and her 6-year-old son in a drunk-driving accident, the UC Berkeley master's graduate admitted the crimes in court.

Rather than face a jury trial, Lumbreras, 25, pleaded no contest and was found guilty of two counts of gross vehicular manslaughter while intoxicated and now faces up to 12 years in prison.

Lumbreras was found guilty of killing his girlfriend, Milanca Lopez, 22, and her son, Xavier, on May 18, 2012, by driving his Cadillac into a tree at about 65 mph.

The accident occurred at the intersection of California Street and Allston Way in Berkeley just after Lumbreras and Lopez picked up Xavier from a baby sitter.

It also occurred after the couple had spent the evening drinking in celebration of their graduations. Lumbreras had just graduated with a master's degree, and Lopez had just graduated with a bachelor's degree. Lumbreras' blood-alcohol level was 0.16 percent, two times the legal limit.

"He has never denied responsibility for the accident, the injuries and the death," said Paul Wolf, Lumbreras' defense attorney. "This is a nightmare, a tragic case all the way around."

Lopez was killed instantly when Lumbreras crashed the 1999 Cadillac, and her son died a week later after family members decided to take him off life support.

Lumbreras spent two months in the hospital with two broken legs and bleeding in his brain before he was taken to Santa Rita Jail on two charges of gross vehicular manslaughter.

Attorneys trying the case were scheduled to select a jury Wednesday, but Lumbreras decided to plead to the counts charged to avoid what promised to be an emotionally devastating trial.

Deputy district attorney Luis Marin said his office accepted Lumbreras plea because it resulted in him being found guilty of the crimes.

"With the plea, we are where we would have been with two guilty verdicts," Marin said. "The trial runs a risk."

Although Lumbreras has taken responsibility, questions about his punishment remain as Alameda County Superior Court Judge Thomas Reardon must decide if Lumbreras gets the maximum 12 years in prison, the minimum of probation or something in between.

Marin said he will request the maximum sentence while Wolf said he will argue for something less.