A state jury found 29-year-old Peter David guilty Thursday of manslaughter, instead of murder, for fatally stabbing his cousin after a night of drinking to celebrate the new year.

David faces a maximum 20-year prison term when he is sentenced in January.

He testified that he stabbed 27-year-old Santhony Albert Jan. 2 in self-defense as his cousin was beating him up in the parking lot of a Waipahu apartment building.

David said Albert had earlier threatened to beat him up at a party with other relatives in Kalihi, then hit him with a sucker punched and hit him in the face with a beer bottle when they continued drinking in Waipahu.

He said he stabbed Albert with an object he found in the parking lot after his cousin knocked him to the ground and was kicking him. He said he doesn’t know what he used to stab Albert, and police did not find the object.

Albert suffered a puncture wound to his left rib area that breached his lung and heart. He had no other injuries. His blood-alcohol content was 0.25, more than three times the legal threshold for drunken driving.

David had a cut on the bridge of his nose, a bruise on his forehead, a black eye and abrasions to his neck and knee.

David said that after he stabbed Albert, he started to run away, then chased after his cousin with two rocks.

The jury also found David guilty of misdemeanor assault of another cousin who stopped him from hitting Albert with the rocks.