Vienna  - Austrian incest father Josef Fritzl was mainly driven by an abnormal yearning to exert power over his victims, who are likely to suffer the consequences of their ordeal all their life, psychiatric and psychological experts say.

The case of Fritzl, 73, who imprisoned his daughter Elisabeth for 24 years and fathered her seven children, was unique in criminal history, the Austrian forensic psychiatrist Gerhard Haller said.

The crimes that Fritzl is charged with - imprisonment, enslavement, rape and incest - are all very much related to power, Haller said: "To control others, to rule over them, to determine their fate."

Fritzl's daughter Elisabeth, 42, and the six surviving children she bore in the 24 years she was being imprisoned and raped by her father could end up living a reasonably normal life, the Vienna psychologist Brigitte Lueger-Schuster said.

However, the expert said the victims would never fully be able to rid themselves of all the traumas they suffered.

Fritzl was a highly intelligent criminal with an abnormal personality that was taken over by a "malign form of self-centredness," according to Haller.

However, the psychiatrist stressed that the man did not suffer from a mental ailment, as he could not have led his complex double life as a respected landlord and rapist over such a long time if he had been ill.

"Someone with a dysfunctional personality has a free will, while the mentally ill does not," Haller said.

Fritzl has asserted that he was treated badly by his mother as a child. Many victims of psychological abuse turned into tormentors, but this did not fully explain his crimes, the psychiatrist said: "Otherwise there would have to be many more Fritzls."

After the long imprisonment and the violence they suffered, Elisabeth Fritzl and her family could regain their well-being to a certain extent, said Lueger-Schuster, who is an expert for post-traumatic stress disorders.

"From the massive traumatic experiences suffered during long years of concentration camp imprisonment, we know that recovery is possible," Lueger Schuster said, "but that the trauma leaves its marks for the rest of the person's life."

People who have suffered extreme violent experiences can suffer from flashbacks, anxiety, depression or psychologically induced pain symptoms.

A post-traumatic therapy such as Elisabeth and her children needed usually includes a combination of psychiatric medications and talking therapy, the psychologist said.

However, Lueger-Schuster said that the children who grew up in Fritzl's dungeon may have developed survival strategies and "a special form of social skills" that would help them cope with their new life as a family in freedom. (dpa)