Austria's most notorious criminal, Josef Fritzl, who imprisoned his daughter in a basement for 24 years and fathered several children with her, will soon undergo psychological tests to determine whether he is eligible for early release from jail. 

Fritzl, 86, was jailed for life in 2008 for keeping his daughter in a soundproof dungeon underneath their family home in Amstetten and raping her thousands of times in a case that shocked the world. 

His daughter and victim, Elisabeth, gave birth to seven of his children over the more than two decades in which she was held captive. 

Fritzl's crimes were only discovered when one of the children, Kerstin, slipped into a coma and was taken to hospital. 

Medical staff found Fritzl's story suspicious and alerted the police, who subsequently reopened the case file of Elisabeth, who had previously been reported missing. 

Despite the life sentence, Fritzl could soon be eligible to apply for early release in 2024 if a psychological assessment deems that he is no longer a danger. 

Up until now, Fritzl has been kept in a special unit for the criminally insane. However, earlier this year, the Regional Court of Krems, a city in Lower Austria where he is imprisoned, made the controversial decision that he should be moved to a regular prison, which would mean he could apply to be released. 

A hidden bathroom at the house and hiding place, where Fritzl imprisoned his daughter. Photo / Getty Images 

The public prosecutor's office appealed and blocked the decision and, as a result, the Vienna Higher Regional Court has been forced to step in and take over the case. 

The Higher Court has said Fritzl must now undergo a psychological assessment to determine his psychiatric and neurological condition, and thus whether he should be moved or remain in place. 

Josef Fritzl is seen during day four of his trial at the country court of St Poelten on March 19, 2009. Photo / Getty Images 

If he is deemed to be "of sound mind" he would be moved to a regular prison, and as a result he would be eligible to apply for early release, as he would have served 15 years – nine years less behind bars than his daughter spent in the Amstetten cellar. 

The psychological expert's opinion is expected by the end of next month, according to Ferdinand Schuster, vice president of the Krems Regional Court. However, it is considered to be unlikely that Fritzl will pass the psychological assessments required to be moved. 

He is said to show signs of dementia and poor mental health. Even if he was deemed psychologically sound and therefore able to apply for early release, his appeal would then have to be granted by judges. 

It is believed that Fritzl, one of Europe's most notorious offenders, planned his crimes for years. He applied for planning permission to construct his underground cellar complex, that would be used as a dungeon, in the late 1970s. When Elisabeth disappeared, he told friends and family that she had run away and joined a sect. Many appeared to believe him. 

While in Krems-Stein prison, one of the largest jails in Austria, Fritzl is said to have been unpopular with other inmates and has spent most of his time in solitary confinement. 

Elisabeth, now 55, lives under a new name in an unknown part of Austria with her children and has not had any contact with her father since he was jailed. 

- by Abby Young-Powell, Daily Telegraph UK