ST. POELTEN, Austria A man accused of imprisoning his daughter for nearly a quarter of a century and fathering her seven children repeatedly raped her in front of the youngsters, prosecutors said Monday as his trial opened in Austria.

Josef Fritzl hid his face behind a blue file folder as a judge began the proceedings under heavy security in St. Poelten, 65 kilometers (40 miles) west of Vienna. Fritzl pleaded guilty to incest and false imprisonment, but only partially guilty to charges of coercion and rape. He pleaded not guilty to murder and enslavement.

Police say the 73-year-old has confessed to holding his daughter for 24 years in a cell he built beneath his home. Investigators say DNA tests show he fathered her six surviving children.

One of the children died in infancy, and prosecutors charged Fritzl with murder, contending the baby might have survived if Fritzl had arranged for medical care.

In her opening statement, prosecutor Christiane Burkheiser accused Fritzl of raping his daughter in front of the children.

Burkheiser said Fritzl didn't talk to his daughter during her first few years in captivity. She alleged that Fritzl once punished the young woman by shutting off electricity to the dungeon.

Defense lawyer Rudolf Mayer appealed to the jury to be objective and not swayed by emotions. He insisted Fritzl was "not a monster."

Fritzl faces up to life imprisonment. A verdict is expected by Friday.

Fritzl's voice was weak and soft as he gave the judge his name and other personal details Monday.

Before the trial got under way, Mayer told The Associated Press his client was nervous.

"He told me, 'I'm scared, Mr. Mayer,'" the lawyer said.

Fritzl eventually removed the folder, but sat still in the dock and stared straight ahead.

Mayer said he had no particular strategy for Fritzl's defense.

Authorities say Fritzl imprisoned and repeatedly raped his daughter, Elisabeth, in the cramped and windowless dungeon he built beneath the family's home in the western town of Amstetten. The crime stunned people worldwide when it came to light last April.

Security was tight in St. Poelten. Police imposed a no-fly zone above the courthouse to dissuade reporters from renting helicopters for aerial shots and to prevent prison breaks from the jail next door where Fritzl has been in pretrial detention.

Mayer welcomed the security, saying both he and Fritzl had received threats over the past year.

Three of the children grew up underground in Amstetten, never seeing the light of day. The other three were brought upstairs to be raised by Fritzl and his wife, Rosemarie, who apparently believed they had been abandoned.

The children, together with Elisabeth, initially recovered from their ordeal in a psychiatric clinic and then were moved to a secret location. Seeking refuge from reporters, they have since returned to the clinic, where security guards are on high alert.

It is the normal policy of The Associated Press to withhold the names of victims of sexual assault, but the identities of two of Fritzl victims have become known. In this case, withholding of the names by the AP became impractical when their first names and the full name of their father were announced publicly by police and details about them became the subject of massive publicity both in their home country and around the world.

None of the victims is expected to testify in court. Instead, the eight-member jury will see prerecorded video testimony from both Elisabeth and one of her brothers, Harald.

In Austria, which does not have the death penalty, murder carries a maximum sentence of life imprisonment. If convicted of enslavement, Fritzl could face up to 20 years behind bars. For rape, he could get up to 15. Incest is punishable by up to one year in prison.

The conviction with the highest penalty will determine the length of the sentence.