A man who pretended to be a Rockefeller was found guilty of the first-degree murder Wednesday of a man whose bones were found beneath a San Marino home. Christian Gerhartsreiter, who used many names including Clark Rockefeller, was tried 28 years after the disappearance of a couple, John and Linda Sohus, in a heavily circumstantial cold case. The authorities said Mr. Gerhartsreiter was a German immigrant who once occupied a guest cottage at the home of Mr. Sohus’s mother. The couple vanished in 1985, and so did he. Linda Sohus was never found, but John Sohus’s bones were unearthed during excavation of a swimming pool. As Clark Rockefeller, Mr. Gerhartsreiter married a wealthy woman. But his identity unraveled when he kidnapped their daughter in a Boston custody dispute. He was close to the end of his sentence for kidnapping when he was charged in the old case.