Musician Graham Coutts yesterday won his House of Lords appeal against his conviction for the murder of schoolteacher Jane Longhurst.
Five Law Lords ruled that jurors should have been offered the possibility of bringing in a manslaughter verdict during his trial.
The matter will now be sent back to the Court of Appeal, which last year dismissed Coutts' appeal, with the invitation "to quash the conviction" and deal with any applications for a possible retrial. Coutts will remain in custody during this time.
Coutts (36) of Waterloo Street, Hove, East Sussex, strangled 31-year-old Miss Longhurst, a special needs teacher originally from Reading, Berkshire, with a pair of tights in March 2003.
Coutts admitted he had been present when Miss Longhurst died, but denied murder, saying her death was an accident during consensual sex.