The man suspected of murdering Leah Croucher spent years in jail for multiple sexual offences against women and children, the BBC has learned.
Miss Croucher was 19 years old when she was last seen in Milton Keynes in 2019. Her body was found in an empty house in the city last month.
Neil Maxwell, who was found dead weeks after the teenager disappeared, was named the prime suspect by police.
Thames Valley Police said it was “keeping an open mind” about the case.
The teenager was last seen on CCTV walking down Buzzacott Lane in Furzton, Milton Keynes, on her way to work on 15 February 2019.