The mother of a prisoner who was found hanged in the segregation cell of a troubled privately run prison after being placed on suicide watch told an inquest yesterday how she repeatedly warned officers of her son's deteriorating mental state. The death of Michael Bailey, 23, at HMP Rye Hill near Rugby in Warwickshire led to the trial and subsequent acquittal of four serving prison officers. A damning inspectors' report in the month after his death found conditions at the jail to be "unsafe and unstable" for both inmates and staff.

The inquest jury heard that prison staff admitted to Carol Bailey that her son had been harming himself after she raised concerns over his unkempt appearance and increasingly erratic behaviour. She told the hearing atIrthlingborough, Northamptonshire, that he had been reciting hymns and had stab marks on his hands and scabs around his neck shortly before his death in March 2005.

She said she had tried to raise her concerns during a series of telephone calls to staff at Rye Hill. "I thought she [a female prison officer] would deal with it, either pass it on or go and check for herself, not just leave it. I was worried, very worried. I was very scared – I did not know what was happening and I had not seen anything like this before with Michael or anybody," she said.

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Two days later, her son, from Ladywood, Birmingham, was found hanged. He was serving a four-year sentence at the prison when he died, the inquest heard. He would have been eligible for parole in November 2005 and due for release in 2006.

The inquest heard that Bailey suddenly changed from being a fit, confident and articulate young man to being subdued and quiet in the days leading up to his death. He was placed on suicide watch after being described as exhibiting "strange" behaviour – including taking his clothes off in the exercise yard, reciting the Lord's Prayer and mumbling incoherently.

Tom Osborne, assistant deputy coroner for Northamptonshire, said: "Over the course of a few days beginning on 18 March 2005 through to 24 March, he went from being a fit young man who was looking forward to being reunited with his family to a man who had become anguished, confused and, at times, violent."

Mr Osborne told the jury that during the inquest, which is expected to last up to six weeks, they should consider if the prison authorities took "reasonable steps" to prevent Bailey from taking his own life.

The inquest was told that Rye Hill had experienced problems with "illicit items" being brought into the category B prison, including drugs and mobile phones. Stephen Hepworth, who was head of operations at the jail at the time of Bailey's death, said when he visited him in the segregation unit on 21 March, and witnessed his "strange" behaviour, he thought that he had taken drugs.

Mr Hepworth, who worked as a suicide co-ordinator at another prison before joining Rye Hill, did not carry out a drugs test or search his cell, the jury heard. When asked why by the family's lawyer, Leslie Thomas, Mr Hepworth replied: "I do not recall why I did not make that decision." Mr Hepworth admitted that, with hindsight, he could have dealt with the situation differently.

The inquest continues.