An ombudsman has identified a catalogue of failings after a man who killed six people including his wife and children died in a maximum security prison.
Damian Rzeszowski, 37, had been serving a 30-year prison term when he was found dead in his cell at HMP Full Sutton, in East Yorkshire, on 31 March 2018. The Prison and Probation Ombudsman (PPO) said there were "deficiencies in staff's management" of the killer.
The Ministry of Justice said that it accepts the PPO's recommendations.
Rzeszowski was jailed for manslaughter by reason of diminished responsibility in 2012 after stabbing to death his wife Izabela Rzeszowska, 30, daughter Kinga, five, and son Kacper, two, at their flat in St Helier, Jersey, following a barbecue in August 2011.
He also killed his father-in-law, Marek Garstka, 56, his wife's friend Marta De La Haye, 34, and her daughter Julia De La Haye, aged five. The PPO's Sue McAllister also said there were "deficiencies in staff's management" of the Prison Service suicide and self-harm procedures - known as ACCT - with staff not carrying out necessary reviews.
She said: "There were several failings in the management of Mr Rzeszowski's time in the segregation unit. Managers failed to record that Mr Rzeszowski was in the ACCT post-closure phase and should therefore only have been segregated if there were exceptional reasons for doing so.
She said prison staff had "failed to take account" that the killer was awaiting an assessment for a transfer to a secure psychiatric hospital and "wrongly concluded that there were no healthcare reasons to advise against segregation".
"In addition, staff did not create a mental health care plan for Mr Rzeszowski, as required for anyone held in segregation for over 30 days," she said.
She said there were also "discrepancies" between prison and healthcare staff's assessment of the level of risk Rzeszowski posed and was concerned by the delay in calling an ambulance when he was found dead.
"Finally, I am concerned that prison staff did not use an interpreter when they informed Rzeszowski's family in Poland that he had died. I consider that this was inappropriate and insensitive." In a statement, the Ministry of Justice said it has accepted all the recommendations made by the PPO. "HMP Full Sutton... continues to improve support for prisoners at risk of self-harm," it said.
It said all staff had been "reminded of using appropriate interpretation services" when contacting a foreign prisoner's family and that the government had invested £100m in prison security to "tackle drugs that can lead to prisoner self-harm".
An inquest jury heard in April that the killer's family complained to a prison officer about Rzeszowski's mistreatment in prison, saying he "should have been in a mental hospital, not a segregation unit" and were attempting to contact the Polish embassy for help.
The jury recorded a verdict of suicide.