St. Poelten, Austria — An Austrian who fathered seven children with a daughter he held captive for 24 years refused to even speak to her for years, coming into the squalid cellar only to rape her, often in front of the youngsters, a prosecutor said Monday.

Wearing a mismatched gray suit and hiding his face behind a folder as the trial began, Josef Fritzl pleaded guilty to incest and false imprisonment, but he denied enslaving his daughter Elisabeth or murdering her newborn son. He pleaded only partially guilty to additional counts of rape and coercion.

The 73-year-old Fritzl faces up to life in prison if convicted of the negligent homicide charge, which stems from the death of the 2-day-old baby boy, who investigators contend might have survived if he had gotten medical care. Incest, by contrast, carries only a one-year sentence.

In her opening statement, prosecutor Christiane Burkheiser portrayed Fritzl as a callous and contemptuous captor who held his daughter in a filthy cramped cellar that didn’t even have a shower or warm water and repeatedly raped her in front of the children.

“For the first years there was no communication … he came, took her, left again,” Burkheiser said.

At other times, she said, Fritzl punished his daughter by shutting off the electricity — plunging the dungeon cell into darkness for days at a time. “Josef Fritzl used his daughter like his property,” Burkheiser said.

“The worst was … there was no daylight,” she said, adding it was also “incredibly humid” and the air was moldy and stale.

Burkheiser said Elisabeth was “broken” by Fritzl’s actions and the uncertainty of her fate and that of her children.

Three of the youngsters grew up in the underground room in the town of Amstetten, west of Vienna, never seeing daylight. The other three were brought upstairs to be raised by Fritzl and his wife, Rosemarie, who was led to believe they had been abandoned by Elisabeth when she ran off to join a cult.

Police say DNA tests prove Fritzl is the biological father of all six surviving children.

Fritzl’s lawyer, Rudolf Mayer, said his client regretted his actions and insisted he was “not a monster,” even bringing his captives a Christmas tree.

“If you just want to have sex, you don’t have children,” Mayer said. “As a monster, I’d kill all of them downstairs.”

Fritzl shielded his face from the cameras with a blue folder as he was led into the courtroom in St. Poelten, 40 miles west of Vienna, then spoke in an almost inaudible voice as he gave the judge his name and other personal details. He eventually removed the folder from his face, but sat still in the dock, staring straight ahead, his hands clasped together.

At one point, his voice breaking, Fritzl briefly recalled his childhood and said life with his mother was “very difficult.” Asked if he had friends, he said simply: “No.”

Fritzl could face up to 20 years behind bars if convicted of enslavement and up to 15 for a rape conviction. A verdict could come as early as Thursday, officials said.

Court spokesman Franz Cutka said Fritzl would have to clarify his partial admission of guilt on the rape counts over the course of the proceedings. Cutka said the partial admission of guilt for coercion was because Fritzl acknowledged he told his victims the cell was rigged to emit toxic gas if they tried to escape, but denied issuing other threats.