An NHS mental health trust “severely underestimated” the risks posed by some of its patients, resulting in the unlawful killings of ten people, a report has found.

Sussex Partnership NHS Foundation Trust has previously apologised for the death of pensioner Donald Lock, who was stabbed 39 times after a collision between two cars in July 2015 by a man with chronic mental health problems.

But a review into nine other deaths has found that the Trust did not learn from its mistakes, sometimes making identical recommendations after deaths had occurred, The Telegraph has reported.

In the case of Mr. Lock, Lewes Crown Court heard that the family of his killer, Matthew Daley, had pleaded with the NHS to get Daley sectioned. Yet the trust failed to carry out a formal assessment for Daley, who suffered from Asperger’s but also showed signs of psychosis.

Daley admitted stabbing Mr. Lock to death, but claimed diminished responsibility and was convicted of manslaughter.

Mr. Lock’s family say he would “still be here today” if the Trust had done its job properly.

But the review found that in seven other cases there was criticism to be made of how the NHS assessed the risk posed by patients.

In some cases, “risks assessments were not completed or were completed incorrectly” and “risk management plans were not completed”.

And in several cases, the process was said to be “inadequate and the risk posed by the service user went unrecognised or was severely underestimated”.

According to the report, “some diagnoses are incorrect and remained unchanged in the face of the service user’s behaviour”.

Some assessments were started but not completed, while others weren’t updated when new information came to light, such as a criminal conviction.

“Sometimes service users made threats to kill others but no further action, for example informing the police or warning the person threatened, was taken,” the report noted.

Policies also tended to view mental health patients only as victims, rather than as potential threats, the report found.

Colm Donaghy, chief executive of Sussex Partnership, offered his “sincere apology and condolences” to the families of victims.

He added: “We commissioned this review with NHS England because we want to make sure we have done everything possible in response to these tragic incidents.

“We have a responsibility to the patients, families and local communities we serve to ensure this. We have investigated each of the incidents individually. We also wanted independent, expert advice about any common themes which may link them.

“Sometimes, as is the case across the NHS, we need to improve processes, policies and training in response to incidents involving our services. But that isn’t enough on its own.

“This review sends us a strong message about the need to identify and embed learning when things go wrong in a way that changes clinical practice and behaviour.

“This goes beyond action plans; it’s about organisational culture, values and leadership.”

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