A jury took just over three hours to reach a unanimous verdicts to find Westland guilty of murdering Liam Deane at the Leeds prison on November 12 last year.
Leeds Crown Court heard John Westland, 29, used a smashed aftershave bottle to inflict the fatal injuries.
It can now be reported that Deane was serving a life sentence for the murder of his two-day old baby daughter.
Westland is a convicted rapist serving an indefinite sentence for a violent sex attack on a 53-year-old woman when he was a teenager.
Deane was found dead by prison officers on the top bunk of his cell after Westland pressed an emergency buzzer.
Opening the case, Peter Moulson, QC, prosecuting, said Westland and Deane shared cell 21 on landing four of the jail’s F wing.
At the time of the alleged attack they were the only two people sharing the cell.
The prosecutor said: “Mr Deane was found dead because someone, say the prosecution, had assaulted him.
“Obviously there is only one candidate.”
The jury of seven women and five men were told that Deane had been attacked by a fragment or fragments of glass from a smashed aftershave bottle.
Mr Mouslon said there was also evidence that Deane had been strangled.
The prosecutor said it was a pathologist’s conclusion that Deane died as a result of the physical injuries he sustained.
The pathologist’s view is that Deane’s injuries were not typical of self-inflicted injury.
The court heard Westland was arrested after Deane’s death and told police in interview: “I murdered him because he is a sex offender”
Westland denied responsibility for causing the injuries when he gave evidence at the trial.
The defendant said Deane was being bullied at the prison and had received death threats from other inmates.