(Reuters) - An Austrian man who held his daughter captive for 24 years and fathered seven children with her could be transferred from a unit for the criminally insane to prison where he would be eligible to apply for release, a court official said on Tuesday.

       The 88-year-old man, widely known as Josef Fritzl but who now has a new name, was sentenced in 2009 to life imprisonment in the special unit. If transferred to a regular jail, he could apply for early release on parole 15 years after his conviction.

       He was convicted of incest, rape, coercion, false imprisonment, enslavement and for the negligent homicide of one of his infant sons.

       An expert opinion on Fritzl's medical condition is being assessed to see if he can be transferred to a regular detention facility, a spokesperson for the regional court of Krems said. Austria's Kronen Zeitung was first to report the expert opinion.

       The court spokesperson said it was unclear how long such an assessment would take, estimating it could range from weeks to a couple of months.

       If transferred to prison, Fritzl's lawyer could in a second step submit an application for early release.

       His lawyer told German daily Bild she had already prepared such an application, adding the aim would be to transfer the man to a nursing home.

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       Fritzl imprisoned his daughter Elisabeth in the basement of the family home when she was 18. Three of the seven children he fathered with Elisabeth lived with her until they were freed in 2008.

       Fritzl and his wife fostered the other three surviving children after Fritzl claimed Elisabeth had given birth to them and then abandoned them to join a religious sect.

       He burnt the remains of the seventh child, who died shortly after birth, in the house furnace.

       (Writing by Nette N？stlinger; Editing by Nick Macfie)