Three vigilantes murdered a convicted child killer by stabbing him more than 150 times after he was released from jail and moved to their town, a jury has been told.

David Osbourne, 51, allegedly plotted the attack after he discovered that his new neighbour, David Gaut, 54, had served more than 30 years in prison for killing a toddler.

It is alleged that Osbourne found out about Gaut after researching him on the internet. Newport crown court heard that another neighbour, Ieuan Harley, 23, said: “I want to chop him up and put him down the plughole.”

Osbourne, Harley and Darran Evesham, 47, are said to have lured Gaut, who was wearing a dressing gown, into Osbourne’s flat in New Tredegar, south Wales, in August last year.

Gaut was stabbed with knives and a screwdriver, his fingernails removed and severe cuts made to his neck after his death, jurors were told.

The accused then dragged Gaut’s body back to his flat and tried to clean up the crime scene, the court heard.

Ben Douglas-Jones QC, prosecuting, said: “After the murder all three men played an active part in moving the body back to his own home. They dragged him down a covered walkway. They cleaned Osbourne’s flat and tried to get rid of bloodied clothing and they set fire to a car to destroy incriminating items.”

Gaut was found by police after another neighbour allegedly heard the men talking about moving the body.

Douglas-Jones said a postmortem carried out by a pathologist, Dr Deryk James, found at least 150 stab wounds to Gaut’s body from at least one knife and a screwdriver.

Douglas-Jones said: “A screwdriver was found in the folds of his dressing gown. The injuries to his neck appear to have been consistent with the screwdriver found in the folds of the dressing gown.

“Many of the stab wounds are consistent with having been made with knives. Dr James found it may be that a larger blade was used to cause the wounds in the belly. He had been clearly stabbed many times until he was dead. Even then, he continued to receive stabbing blows.

“All three wanted him dead. They encouraged each other and played their parts in the lead-up to the murder. Mr James found his fingernails had been cut off after he died.”

Douglas-Jones told the jury: “The murder in this case was brutal. The deceased, Mr Gaut, himself committed a violent offence. It is no part of our function to judge him for that. He was judged by a jury all those years ago. He was sentenced and he served that sentence.”

Gaut was jailed in 1985 for the murder of his girlfriend’s 17-month-old son, whom he had been babysitting. He was released on parole in November 2017.

The court was told police were alerted by another friend, Michael Lewis. After visiting a pub, Lewis and the defendants allegedly returned to Osbourne’s flat.

Believing Lewis to be asleep in a chair, they began discussing the murder of Gaut, whom they knew as Dai, the court was told.

Douglas-Jones said: “Mr Lewis will say that he heard the three defendants talking about the fact that Harley had killed Dai because he had murdered a child, and after Harley stabbed him they cleaned up.

“He specifically remembered one of the three men saying in the presence of the others: ‘We’re gonna have to cut him up and take him to ... get rid of him, like, you know what I mean’.”

One of the defendants said they did not have the tools for that. “There was talk about cutting fingernails off, flushing them down the toilet, a discussion about throwing a thumb in the river,” said the prosecutor.

The court heard the day before the alleged murder Osbourne’s mobile telephone was used to conduct online searches for “registered sex offenders”.

The day after the alleged murder, Harley visited two other neighbours and spoke about Gaut, with Harley telling them: “Don’t worry. You won’t be seeing him again,” said the prosecution.

Douglas-Jones told the jury: “In the same way that you would carry out your task if you were dealing with the murder of a gangster who had killed many people, you have to stand back from any reduced sympathy you might naturally have for the deceased given his historical crime and assess the quality of the evidence.”

Osbourne, Harley and Evesham, all of New Tredegar, deny murder. Evesham and Harley also deny perverting the course of justice. The trial is expected to last four weeks.