A killer who thrust a machete into his friend's heart had a history of carrying knives and being violent.
Paul Largan, who attacked Jason Gregory during a row at his home, also once claimed he would stab someone in the neck.
Both men were the subjects of mental health treatment, with Largan having been diagnosed with paranoid schizophrenia.
His history of violence and threatening behaviour was detailed in a recently published NHS assurance report following investigations to establish whether lessons could be learned from the tragedy.
Twelve areas for action were ultimately identified, seven of which called for a review of the function of the St Helens local recovery team.
"Good progress" was said to have been made in relation to each of those recommendations by September of last year.
Mr Gregory was stabbed on July 2, 2017, at Largan's home on Napier Close in St Helens.
In May 2018, Liverpool Crown Court heard the 35-year-old had battled paranoid schizophrenia for years and believed his friend Mr Gregory, 46, had been conspiring against him.
John Benson, QC, prosecuting, said an argument took place in the flat and Mr Gregory, who had been drinking, was told to “f*** off” and ejected through the front door by Largan.
But CCTV footage showed Mr Gregory lingering outside the house, banging on the door and shouting through the letterbox.
Mr Benson said: “The defendant’s response to the deceased making a nuisance of himself was to arm himself.
“He opened the door and the deceased tried to enter, but immediately recoiled.”
The court head Mr Gregory collapsed and would have died rapidly.
Largan had closed the door but emerged a short while later, with CCTV footage capturing him vomiting.
Three psychiatrists agreed Largan had been unable to exercise self control or form a rational judgement when he carried out the attack.
Nigel Power, QC, defending, said his client had been asked by a psychiatrist after his arrest what he thought about the offence.
He said: “He said I’m really sorry, it hurts me what I have done. He’s my mate. If I had been less paranoid I would probably have hit him not stabbed him.”
Judge Alan Conrad, QC, accepted Largan was "seriously unwell at the time” and made him the subject of a hospital order under Section 37 of the Mental Health Act after his plea of manslaughter with diminished responsibility was accepted.
As part of the NHS review, investigators delved into Largan's past use of mental health services, which started on May 18, 2004.
The period examined continued until July 3, 2017 when the report stated those involved were informed "of service user A’s arrest for attempted murder".
The report noted: "The clinical records for service user A demonstrate a prolonged pattern of physical violence, a propensity to use and carry knives for protection or to threaten or use against other persons, detail 14 different convictions, including assaults on police, and driving whilst under the influence."
One of the recommendations made following initial inquiries was for a specialist group to "review the function of the recovery team" because it had not been established whether a psychiatrist was ever told Largan had once claimed he "would stab someone in the neck".
The independent review focused on the work of North West Boroughs Healthcare NHS Foundation Trust.
Concluded in September 2020, it found: "The trust has provided extensive evidence that learning from this incident has influenced the development of systemic changes through a wider trust-wide transformation initiative with a phase two action plan taking this forward.
"The trust has demonstrated good progress with all the recommendations. It should now take steps to assure itself that all recommendations have been implemented fully, changes in practice have been successfully embedded, and where possible, can demonstrate improvements in practice."
North West Boroughs Healthcare no longer exists as an NHS trust, with its Merseyside services transferred to Mersey Care NHS Foundation Trust at the beginning of this month.
A spokesman for Mersey Care said: “We welcome the publication of the independent investigation into the historic care and treatment of mental health service user A and send our condolences to their family and friends at this difficult time.
“On June 1, 2021, Mersey Care became the new provider of these services following the acquisition of the former North West Boroughs Healthcare NHS Foundation Trust.
"We are therefore unable to comment on the tragic events from several years ago which led to the commissioning of this report.
“We are an organisation that prides itself on care needs assessment and collaborative working practices for patients and we are confident our larger Mersey Care will become stronger for our collective commitment to the highest standards of healthcare."
