The night Matthew Shettles graduated from high school, he had sex with his girlfriend. He became a sex offender. He was 18 and she was five weeks shy of 15, when a three-year age difference would have made the act legal. The girl confided in a counselor, who reported Shettles. He was convicted of a misdemeanor and given three years’ probation, community service, a $1,600 fine and his name on a registry of sex offenders for life.