Marjorie Wallace from the charity SANE says procedures appear to have been lacking
An investigation into the care received by a mentally ill man who murdered a police officer in Bedfordshire has revealed "serious failings".
Ikechukwu Tennyson Obih, 29, stabbed Pc Jon Henry in Luton in June 2007.
Bedfordshire and Luton Mental Health Trust conducted an investigation into Obih's care but did not make it public.
After a Freedom of Information Act request by BBC Three Counties Radio, it was revealed the trust had poor communication, management and training.
Obih, of Winsdon Road, Luton, denied murdering Pc Henry but admitted killing him on the grounds of diminished responsibility. He was found guilty of murder at Luton Crown Court in March.
He was also found guilty of attempting to murder a window cleaner.
Obih, who had been detained in the secure mental hospital in Rampton, Nottinghamshire, since his arrest was suffering from paranoid schizophrenia at the time of the attack, his defence team said.
The court was told he was diagnosed with the condition in 2005 after suffering problems from abusing alcohol and cannabis.
Three Counties Radio has appealed against the decision by the trust to withhold key information into the case.
The Bedfordshire and Luton Mental Health Partnership Trust said it had a serious duty to obtain a balance between public openness and patient confidentiality.
It added in a statement: "The Trust extends its deepest sympathies to people affected by the tragic events in Luton Town Centre two years ago.
"The Trust is now under new interim management and many major improvements are being made to services across the organisation.
"The Trust is co-operating fully with the East of England Strategic Health Authority's independent investigation of the events which took place in 2007."