Merseyside Police can confirm that officers from the specialist Matrix Serious Organised Crime team are investigating the murder of a 35-year-old prisoner at HMP Altcourse on Friday, 14 November 2014.
A 41-year-old prisoner from the prison has been arrested on suspicion of murder.
Officers were called to the prison at about 11.10am on Friday, 14 November 2014, following a report that a man had been assaulted.
The victim was taken to Aintree University Hospital, where he was pronounced dead a short while later.
The family of the victim has been informed and a Home Office post mortem will be carried out to establish the cause of death.
The arrested male has been taken to a police station on Merseyside where he will be interviewed by detectives.