The family of a woman who was killed by a man suffering from a psychotic illness have said "she might be alive today" if he had been managed properly.
Martin Bell, 45, beat Gemma Simpson to death with a hammer in 2000 and hid her body at a beauty spot near Harrogate.
In 2014, he walked into a police station and confessed to her murder. He was later jailed for manslaughter.
An independent report by NHS England said that Miss Simpson's death was "not predictable nor preventable".
Bell had been sectioned in a hospital for about nine months in August 1999 and was released around six weeks before he killed Miss Simpson.
In a statement, Miss Simpson's family said they broadly welcomed the findings of the NHS investigation, but had "some reservations".
The family said: "In 2000 Martin Bell was known to carry a knife, was delusional and recognised as a real risk to others, yet he was able to be released without any effective package of care, monitoring, or even a proper assessment of how the risks he posed to others would be managed.
"We believe that if he had been managed properly, Gemma might still be alive today."
The report, which said its authors were severely hampered by a lack of medical records, concluded: "It appears possible that, if MB (Martin Bell) had been fully compliant with anti-psychotic medication and had refrained from misuse of cannabis, then he may not have suffered from a relapse of his psychotic illness.
"In these circumstances, the death of Gemma Simpson might have been prevented."
Doctors had considered Bell's cannabis use may have contributed to or exacerbated his illness, and that he had smoked the drug on the day he killed Miss Simpson.
But it said "there were no actions that clinicians could have specifically taken to enforce the continuation of medication...nor to enforce his abstinence from cannabis."
Bell's trial at Leeds Crown Court in 2014 heard that he struck Miss Simpson an "uncountable" number of times with the knife and hammer in a "frenzied" attack at his Harrogate flat, before leaving her body for four days in a bath.
He then sawed off the bottom of her legs so she would fit in the boot of a hire car before burying her at Brimham Rocks, near Harrogate.
Bell admitted manslaughter on the grounds of diminished responsibility and was jailed for 12 years.