Obih was diagnosed with paranoid schizophrenia in 2005
A man has been jailed for life and told he will serve at least 25 years for the murder of a police officer.
Ikechukwu Tennyson Obih, 29, stabbed Bedfordshire Pc Jon Henry twice in the chest as he tried to arrest him in Luton town centre on 11 June 2007.
Obih, of Winsdon Road, Luton, denied murdering Pc Henry but admitted killing him on the grounds of diminished responsibility.
He was also found guilty of attempting to murder a window cleaner.
The 36-year-old policeman was one of four officers called to George Street, Luton, after window cleaner Stephen Chamberlain was stabbed, Luton Crown Court heard.
Pc Henry was stabbed as he tried to arrest Obih, who then lashed out at another window cleaner, David Knight, leaving him injured.
A large baton round fired by an armed response team failed to stop him and it was only when he was stunned for the second time by a Taser gun that the officers were able to overpower him.
No amount of anger or hate can change what he has done to us
Mary Henry, Pc Henry's widow
Pc Henry's daughter, Maggie, was 11 months old when he was killed. In a victim impact statement his widow, Mary Henry, said her husband's death was "like losing a limb".
She said: "I felt lost. I was often asked how I felt about the offender and whether I was angry and I wasn't. I felt numb."
Obih, who has 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.
Pc Jon Henry was wearing a stab-proof vest but it was not done up to the top
The court was told he was diagnosed with the condition in 2005 after suffering problems from abusing alcohol and cannabis.
However, the prosecution said Obih was not in an acute phase of the illness at the time of the attacks.
Mrs Henry told of the moment she heard of her husband's death: "I was upset but very calm. I think I was in shock. I think I had a million things running through my mind. I didn't know what to do.
"I felt totally in limbo, like I was in purgatory."
She said of Obih: "No amount of anger or hate can change what he has done to us."
it is possible that it will never be safe to release you at all
Mr Justice Bean
Mrs Henry said she married her husband in 2005, five years after they met. She described her wedding day as the "happiest day of my life".
Obih was also found guilty of aggravated burglary, assaulting a neighbour occasioning actual bodily harm, attempting to murder Mr Chamberlain and wounding a second window cleaner, David Knight with intent. The jury found him not guilty of attempting to murder Mr Knight.
Jailing Obih, Mr Justice Bean said: "Pc Henry was a dedicated and courageous officer who gave his life upholding the rule of law and protecting the people of Luton and the danger you posed.
"The killing of a police officer doing his duty is fortunately still a rare event in Britain and it has also been viewed with a particular abhorrence by the law-abiding public.
"You are at present a highly dangerous man and there is a very serious risk to the public of your committing further specified offences of violence if released. Indeed, it is possible that it will never be safe to release you at all."
Killer Tennyson Obih filmed in Luton town centre just moments before he was stopped
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