A judge found Alberto Martinez guilty of murder in a bench trial that concluded Monday. He faces a life term when he's sentenced July 30.
Cape May County prosecutors said Martinez struck 19-year-old Vincent DeSario in the head with a baseball bat in May 2010 in Wildwood.
DeSario was with a group of men walking along the street when one of them tripped, causing them to laugh.
Witnesses said Martinez angrily approached the group and swung the bat, hitting DeSario. He was initially charged with aggravated assault. The charge was upgraded after DeSario died two weeks later.