A man who murdered a retired CPS lawyer and carried out a campaign of violence against cats planned to carry on killing vulnerable gay men, a court has heard.

David Iwo, 23, laughed as he was sentenced to a minimum of 33 years at Preston Crown Court on Wednesday for the murder of Martin Decker, 69, who was bludgeoned to death with a hammer at his home in Birkenhead, Wirral, on March 6.

Alan Kent QC, prosecuting, said the murder was part of a campaign of violent robberies of vulnerable men.

He said: “Had he not been caught he would have killed again and would not have stopped until he was caught.”

He said Iwo was also accused of the torture and mutilation of 30 cats in the Norfolk area, but after he was “uncooperative” at a plea hearing earlier this month a decision had been made not to proceed with those charges.

The court heard Mr Decker, who worked for CPS Mersey Cheshire as a senior lawyer from 1986 until he retired in 2012, had contacted Iwo in March after seeing his advert offering sexual services on the app Vivastreet.

Iwo, who appeared via video-link from HMP Manchester, later told police he  arranged to go to Mr Decker’s home in Vyner Croft on Saturday, March 6 and they had agreed he would be paid £250.

He armed himself with a hammer and travelled from Liverpool to Wirral with the intention of murdering Mr Decker, the court heard.

In police interview, Iwo said he had shaken hands with Mr Decker, who offered to get him a drink, and when he turned his back to him Iwo had struck him with the hammer repeatedly.

Sentencing him, Mr Justice Jacobs said: “You showed no mercy at the time and you have never shown any remorse subsequently.”

Iwo, of no fixed abode, then searched his victim’s clothing and home and took cash, alcohol and valuable electrical items from his house.

He was arrested at a hotel in London on March 10 and pleaded guilty to the murder at a hearing in September.

He told officers he didn’t view Mr Decker as a human but as “an objective”, and saw the murder of a human as a “progression of his habit of killing cats”, Mr Kent said.

He also said he had attempted to strangle a man the week before.

Mr Justice Jacobs said: “You attacked gay men, confident they were not going to report an attack.”

In a letter to a psychiatrist, Iwo said he enjoyed a life “operating outside of the law”.

He said he had enjoyed watching cats struggle and described various ways he had tortured and killed the animals, becoming known as the “NR3 cat killer”.

The court heard that Iwo told police and psychiatrists he had made a conscious decision to live his life by killing and stealing from people who approached him for sex and he would go on until he got caught.

A psychiatric report found he had dissocial personality disorder and was highly narcissistic, with little or no capacity to experience guilt or remorse.

Iwo refused to have legal representation during the hearing, telling the judge: “I do things for myself, if I let someone else do things for me I would be dead.”

When asked if he wanted to make any points Iwo, who was smiling as some of the facts of the case were outlined, said: “I’ve got nothing to say.”

In a statement read to the court, Mr Decker’s brother, Jeremy, who discovered his body the day after his death, said: “Martin deserved so much better. He was a lovely man who was taken from us all.”

He said their 88-year-old mother relied on him and he doubted she would ever recover from the loss.