LONDON - A teenage girl was convicted yesterday of committing a murder when she was just 12. Sharon Carr, now 17, was found guilty at Winchester Crown Court of the murder of a trainee hairdresser, Ms Katie Rackliff (18), whose half-naked body was found near a cemetery in Farnborough, Hampshire, on June 7th, 1992, by two schoolboys. She had been stabbed at least 29 times with a six-inch bladed knife.