A golden boy becomes a killer -- a brain defect may be the reason.

Sabrina Gonsalves and John Riggins were both 18 years old in the summer of 1980, about to start college and in love. On Dec. 20 of that same year, the couple was brutally murdered, both with their throats cut, on a foggy night in their hometown of Davis, Calif., on their way to Gonsalves' sister's birthday party. Now, more than 25 years later, the birthday gift the couple had with them may help identify the killer.