A Stevenage man who murdered three people in a machine gun attack has been cleared of the attempted murder of two prison guards and the wounding with intent of a third.

Kevan Thakrar, 24, who is serving a life sentence for the drug-related murder of three men and the attempted murder of two women in 2007, admitted stabbing the guards with a broken bottle in March last year at Franklands Prison, County Durham, but claimed it was self-defence.

The court heard he was suffering from post-traumatic stress disorder as a result of his prison experiences. Thakrar claimed he attacked the officers in self-defence in a “pre-emptive strike” after ill-treatment and abuse at the high-security prison. He said the abuse stemmed from a culture of racism and victimisation at the prison. Officers denied this.

Thakrar, formerly of Lomond Way, said he was sorry the guards were hurt, but added “it should not have come to that”.

A jury at Newcastle Crown Court cleared him of all charges yesterday (Wednesday).

Ex-Frankland governor David Thompson, who was in charge at the time of the attacks, criticised the verdict.

“Staff at Frankland and elsewhere across the service will feel let down, dismayed and humiliated by part of the criminal justice system in which they serve.

“Colleagues in other professional agencies have expressed their dismay at how a case like this can be conducted in a manner where the victims feel they are on trial, that they have done something wrong, and then for the assailant to be exonerated.”

He added two of the guards, Craig Wylde and Claire Lewis would not work in the prison service again, while Neil Walker had saved Ms Lewis from worse injuries by intervening.

The judge, Mr Justice Simon expressed sympathy to the injured guards. He said: “It was not part of the defence case in any way that they brought their injuries upon themselves.”