Austrian authorities have today begun interviewing Elisabeth Fritzl, the woman held captive in a cellar for 24 years by her father, Josef.
The interview is being filmed so Elisabeth will not have to give evidence in person at her father's trial, officials have said.
A doctor is participating in the questioning to help police to discover how one of the seven babies she was forced to bear by her father died, prosecutors said.
Police expect to be ready to lay formal charges against Josef Fritzl within a few months, and his trial could start later this year.
He is expected to be charged with incest and abduction but could also face a murder charge if found responsible for the death of the baby – one of twins born to his daughter in 1997.
Police said Fritzl had already admitted incinerating the infant's body but it is not clear exactly how or why the baby died.
According to prosecutors, Fritzl has confessed to keeping his daughter captive in an underground cellar complex at his home in Amstetten, where he says he had seven children with her.
Three of the children were confined to the cellar, three were raised above ground by Fritzl and his wife. The other died in infancy.
DNA tests have proved he is the father of Elisabeth's six surviving children.
The case came to light after one of the children he fathered, Kerstin, became seriously ill and was taken to hospital.
He only released Elisabeth, now 42, from her underground prison after doctors appealed for the sick teenager's mother to come forward because they were unable to find her medical records.
Elisabeth then told police of her ordeal.
Kerstin, who was in a coma until earlier this month, is expected to make a full recovery.
Elisabeth and her children are undergoing treatment at a psychiatric hospital.
One of the three children raised above ground, a 15-year-old girl, left the clinic to take part in a four-day youth fire brigade camp along with 4,000 other teenagers, an Austrian paper has reported.
Fritzl is being held in pre-trial detention in St Poelten, 80 km (50 miles) west of the capital, Vienna, while police assemble the case against him.