The jury in the trial of two prisoners accused of murdering the disgraced former Lostprophets singer Ian Watkins has been discharged for legal reasons.

The judge at Leeds crown court told jurors on Friday that there would be a retrial. “Very reluctantly, I’m going to discharge you and the case will have to be retried,” said Mr Justice Hilliard.

“That’s disappointing for you and for everyone.”

The defendants, Rico Gedel, 25, and Samuel Dodsworth, 44, both denied murdering Watkins and possessing a makeshift knife in prison. The court heard evidence about the stabbing of Watkins at high-security HMP Wakefield, where he was serving a 29-year sentence for child sexual offences.

Gedel allegedly used a homemade weapon to attack Watkins in his cell before he died. Prosecutors say that immediately after the stabbing, Gedel left the cell and handed the makeshift knife to Dodsworth, who then disposed of it in a bin.

The prosecution’s case has been that both men were jointly responsible for Watkins’s death, alleging Dodsworth, who is serving a sentence for raping a woman, had been aware of the planned attack and assisted by helping to conceal the weapon. Dodsworth, however, has denied any involvement in the killing, insisting he was not part of any plan and came into contact with the weapon only after the incident, before panicking and throwing it away.

Gedel told the court he disliked being housed with sex offenders at Wakefield. He said he had chosen Watkins because of “proximity”, as he had been placed in the neighbouring cell the night before the attack.

He also told the jury that “part of him” had wanted to kill Watkins, while another part had not. “Sometimes what your heart wants is not what your brain wants,” he said.

Prosecutors said the attack took place shortly after prison officers began unlocking cells on the morning of the incident.

Prosecutors told the jury both men were guilty of murder because Dodsworth “knew the attack was going to happen”, though they argue the stabbing was carried out by Gedel. The defence has maintained that Dodsworth was simply in the wrong place at the wrong time, and that he reacted in panic after unexpectedly being handed the knife. Gedel’s evidence, meanwhile, acknowledged feeling jealous of “nonce prisoners” who got “treated like royalty”, but did not formally accept guilt of murder.

Watkins was jailed for 29 years in December 2013, with a further six years on licence, after admitting to a string of sexual offences, including the attempted rape of a fan’s baby. With the jury now discharged, the case will be listed for a retrial at a later date, meaning the allegations against both men remain unresolved before the courts.