NHS managers have apologised for allowing a man to discharge himself from a psychiatric unit before stabbing another man to death in 2002.
Dale Pick, a paranoid schizophrenic was allowed to leave despite warnings he represented a "real risk of violence."
Eight days later he killed Michael Doherty in an alley in Leicester.
An independent report into the care of Pick said he was discharged against a background of bed shortages at the Leicestershire Partnership NHS Trust.
The report by the Leicestershire, Northamptonshire and Rutland Strategic Health Authority revealed a catalogue of errors.
In a statement, Sir Richard Tilt, chairman of the authority said: "This is a tragic case and one which we must learn from.
"It is clear that some aspects of the care provided to Mr Pick by the mental health service could and should have been better - for this I offer a full apology."
According to his mental health records, Pick was known to carry a knife and had made threats to kill his girlfriend.
During his final admission to hospital he also threatened to slash a male nurse's throat with a broken cup.
Despite this and following treatment progress, after a month's care at the Bradgate Mental Health Unit, he was allowed home on extended leave.
He was later discharged, even though Pick's community psychiatric nurse expressed continuing concerns that there appeared to be little change in his mental state.
Pick, who was convicted of manslaughter on the grounds of diminished responsibility, was ordered to be detained under a hospital order by the courts following the death of Mr Doherty who was stabbed eight times in the head and heart.