Jerves' partially clothed body was found by tourists later on the morning of her death, near a pair of abandoned cars and next to an old graveyard at the Glass Beach area of Port Allen. She had been stabbed repeatedly.

Defense attorney William Feldhacker said that many of Jerves' injuries could have been incurred as she tried to regain control of a knife that Costa had allegedly taken away from her.

"There certainly is evidence of self-defense in this case," he said.

Pathologist Dr. Anthony Manoukian described several wounds on Jerves' body that he termed defensive in nature — wounds to the hand and arms, which he said were consistent with someone trying to defend against a knife attack. But he also said that these were not the ones that caused her death.

Manoukian said she could have died from bleeding from any of four stab wounds to her back, which entered her lungs, or from a deep wound to her neck that cut major veins and arteries.

"One of the wounds to the neck and the wounds to the back, taken by themselves, would have been fatal," he said.

Detective Sam Sheldon said that Costa was questioned twice by police. Once on the day of the slaying, he admitted giving Jerves a ride but not to killing her. When questioned again on Jan. 16, he confessed to killing her and provided extensive detail about the 18-year-old's death, Sheldon said.

Detective Larry Stem told the court that Costa had volunteered to take investigators to where he allegedly threw the murder weapon. Stem said that following Costa's instructions, police located a knife with a 4- to 5-inch blade at Glass Beach.