A new report has called on the British government to consider changing the law on homicide following the Valdo Calocane case.
Calocane killed university students Grace O'Malley-Kumar whose mother is Irish and Barnaby Webber, both 19, and 65-year-old school caretaker Ian Coates in June 2023.
He pleaded guilty to manslaughter on the grounds of diminished responsibility after he stabbed the three people to death in Nottingham and tried to kill three others.
Families of the victims criticised the fact that prosecutors accepted a plea of guilty to manslaughter.
However, five different psychiatrists said he had been suffering a psychotic episode at the time.
A review of the decision by the Crown Prosecution Service (CPS) to accept the manslaughter plea was ordered by the Attorney General Victoria Prentis.
The CPS Inspectorate (HMCPSI) examined the case and found that the law had been correctly applied by the prosecution.
However, it said the government should examine whether the homicide law should be considered in three tiers, as recommended by the Law Commission in 2006.
This would make three tiers of charges available to prosecutors - first degree and second-degree murder, as well as manslaughter.
Inspectors found that if the 2006 recommendations had been accepted and implemented, "the unlawful killings in this tragic case would have been categorised as murder, albeit second-degree murder".
It also called for the government consider whether diminished responsibility should reduce an offence from murder to manslaughter.
The report also said the families of the victims could have been better supported during "an incredibly difficult process".
The prosecution said the families had been consulted about the manslaughter plea but Barnaby Webber's' mother, Emma Webber, said after the trial that the families had been presented with a "fait accompli".
She said they had been "railroaded".
Trial judge Mr Justice Turner said when he imposed an indefinite hospital order on Calocane last January, that it was unlikely the defendant would ever be released.
The judge said if he had sent him to prison the sentencing guidelines would have meant a prison sentence of just 13 years and four months.
After today's report was released Chief Inspector of the HMCPSI Anthony Rogers said: "It is unimaginable having to deal with the death of a loved one under such horrific circumstances, but having to deal with the criminal justice system at a time of heartbreak and grief adds a further dimension of challenge".
"To better support victims and increase public trust, we call on the government to consider amending the homicide law, review the support provided to victims of crime in serious cases such as this, and provide greater clarity about the role of victims in the criminal justice system."
