"This is the saddest case this court has ever had to consider," Alameda County Superior Court Judge Alfred A. Delucchi said as he sentenced former San Francisco Policeman Fred Kilmer, 31, to three years in state prison for his guilty plea to a charge of molesting an 11-year-old boy in 1984. Delucchi ordered that the two-year police veteran be placed in "super protective custody" in the state prison. Roy Neuman, a children's counselor, said the victim, now 13, is in "guarded" emotional condition, and is being harassed in school because of the possibility he may have contracted AIDS from the defendant. Deputy Dist. Atty. Ken Burr said Kilmer met the boy through the youngster's older brother, with whom the defendant had a sexual relationship. "And the brother died of AIDS," Burr said. The Hayward case unfolded during an investigation of Kilmer in a Tulare County incident in which he pleaded guilty to soliciting a 14-year-old to engage in lewd conduct.