Josef Fritzl, who was jailed for raping and holding his daughter captive for 24 years, will not be transferred to a regular prison.
The 88-year-old had applied for a transfer to regular prison, arguing that as an elderly, frail man he no longer poses any threat.
Fritzl has been in a prison for "mentally abnormal" inmates since his conviction in 2009 for incest, rape, enslavement, coercion and the murder, by neglect, of his newborn son in a dungeon he secretly built under his house.
A court in the town of Krems an der Donau ordered the transfer to a regular prision in January. However, prosecutors filed a complaint aimed at overturning that decision to the Vienna Higher Provincial Court.
Defendant Josef Fritzl is pictured during proceedings on the last day the last day of his trial in 2009
Reuters
A spokesperson from the Vienna court said in a statement: "Unlike the court of first instance, the Vienna Higher Provincial Court came to the conclusion that the facts necessary for such a conditional release had not yet fully been established."
It added that it had overturned the decision of the lower court in Krems and ordered the lower court to establish more facts before reaching a fresh decision.
A spokesman for the lower court in Krems said of the Vienna court's ruling: "A supplement to the medical report and a new hearing of the detainee at the end of April were ordered."
From regular prison Fritzl would be able to submit a request to be released from prison altogether.
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The house where Josef Fritzl imprisoned his daughter in a cellar for 24 years and fathered seven children with her
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Fritzl raped his daughter Elizabeth and held her captive for 24 years, fathering her seven children. The case attracted worldwide attention when it came to light in 2008.
He was found out in 2008 when Elisabeth's 19-year-old daughter Kirsten became critically ill. After Fritzl took her to hospital, police issued an appeal for Elisabeth to come forward.
It was only when questioned by police, did Elisabeth reveal she had been held captive for over two decades.
Fritzl was jailed for life in 2009 after he was convicted of rape, incest, enslavement and negligent homicide. The 88-year-old has now changed his name to one that has not been made public.
Josef Fritzl was sentenced to life in prison
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He is suffering from advancing dementia but he was able to follow the brief proceedings in January when his conditional release was ordered, his lawyer Astrid Wagner told reporters after that hearing.
In the years that followed his arrest, he told The Sun that he believes he will be forgiven by his family, saying: "I miss my family very, very much. I am sure that we are going to be reunited and I think they are going to forgive me for what I have done."
Fritzl also told reporters he watched the coronation of King Charles on TV, saying it was "splendid".
He added: "I'm a monarchist. I'm a big fan of King Charles."