Moors Murderer Ian Brady is undergoing a series of tests after becoming "acutely physically unwell".
The Glasgow-born killer is due to attend a mental health tribunal on Monday regarding his application to be transferred to a Scottish prison and be allowed to die.
But his appearance at that hearing is now in doubt after he was taken ill at the high-security Ashworth Hospital in Merseyside where he has spent the last 25 years.
A hospital spokesman said on Tuesday: "Ian Brady, a patient at Ashworth Hospital, has been admitted to a general hospital after becoming acutely physically unwell on the ward. He is undergoing a series of tests and, as a precaution, he will be kept in.
"Ian Brady, 74, is in a single room and will be accompanied in that room at all times by two nurses from Ashworth Hospital. Two other members of Ashworth Hospital staff will also be on duty outside his room throughout his stay in the general hospital.
"It is too soon to provide a comment about his condition."
Brady has been tube-fed since refusing food 12 years ago.
His solicitor, Richard Nicholas, confirmed his client was in hospital but said he could not comment any further on what happened.
He said the tribunal "was obviously very important", adding: "We are waiting for a decision. We hope it's not going to be affected."
Brady and his partner, Myra Hindley, were responsible for the murders of five children in the 1960s.
They lured children and teenagers to their deaths, with victims sexually tortured before being buried on Saddleworth Moor above Manchester.
Pauline Reade, 16, disappeared on her way to a disco on July 12 1963 and John Kilbride, 12, was snatched in November the same year.
Keith Bennett was abducted on June 16 1964 after he left home to visit his grandmother; Lesley Ann Downey, 10, was lured away from a funfair on Boxing Day 1964; and Edward Evans, 17, was killed in October 1965.
Brady was given life at Chester Assizes in 1966 for the murders of John, Lesley Ann and Edward.
Hindley was convicted of killing Lesley Ann and Edward and shielding Brady after John's murder, and also jailed for life.
In 1987 the pair finally admitted killing Keith and Pauline.
Both were taken back to Saddleworth Moor in 1987 to help police find the remains of the missing victims but only Pauline's body was found.
Hindley died in jail in November 2002, aged 60. Brady wants to be transferred to a Scottish prison and be allowed to die.
The mental health hearing, due to be held on July 9, could be a rare chance to see the Moors Murderer in public.
It is only the second time that such a hearing has been held in public.
The tribunal is due to take place at the hospital and be relayed to the Civil Justice Centre in Manchester, where the public will be able to observe the proceedings, Judge Robert Atherton ruled.
- Moors Murderer Ian Brady wants to move to Scottish prison to die
- Moors Murderer Ian Brady wants move to Scottish prison
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