The family of a vulnerable man murdered by a drug addict say the coroner and other authorities have failed to undertake a "full and fearless investigation" into his death.
Christopher Laskaris was stabbed through the heart by Philip Craig at his flat in Leeds in November 2016.
At the end of the inquest, coroner Jonathan Leach concluded the 24-year-old was unlawful killed.
A family statement said the findings had "only deepened our distress".
Fiona Laskaris has campaigned to find out why her son was not properly diagnosed with autism or given more support in the community.
The family also believes police left him at risk by not making sure his flat was secured after officers smashed in his front door days before Craig killed him.
Mr Leach ruled both issues were beyond the scope of the inquest at Wakefield Coroner's Court.
In a statement read by barrister Jake Richards, the family said Mr Laskaris was a "bright, lovely boy, missed by us every day".
It added: "We are incredibly disappointed and angry that the coroner decided not to investigate the failure of local services to properly diagnose and assess Christopher, or investigate how he came to be living in a flat, without support, vulnerable to abuse and exploitation... which ultimately led to [his] death.
"We have no answers as to why the police didn't ensure Christopher's door was appropriately secure. This allowed a drug-taking killer to simply wander into his property.
"The failure of the coroner, the police, local services and government... to undertake a full and fearless investigation into Christopher's death has only deepened our distress."
Philip Craig was jailed for life for murder in May 2017 and told he must serve a minimum of 25 years.
He had been released from prison on licence in February 2016, recalled to prison three months later, but released again in September 2016.
Mr Leach ruled that to the knowledge of the private probation provider, Craig had not done anything that justified his further recall to prison.
West Yorkshire Police said officers responding to an incident entered Christopher Laskaris' flat on 8 October 2016.
"After Christopher was removed from the property, officers remained until the premises was made secure," the force said.
"Christopher was a vulnerable adult who was unlawfully killed by Philip Craig, a drug dealer and drug user. A thorough investigation was carried out into Christopher's death, which resulted in Craig being convicted of murder and jailed for life.
"The coroner commended Det Supt Mark Swift and his team for bringing Craig to justice."
Leeds City Council has been contacted for its response to the family's remarks.