ST. POELTEN , Austria -LRB- CNN -RRB- -- A verdict in the case of Josef Fritzl , the Austrian man accused of keeping his daughter in a cellar for decades and fathering her seven children , could come as early as Thursday , a court official told reporters Monday . Josef Fritzl expects to spend the rest of his life in prison , his attorney has said . As his trial began behind closed doors Monday Fritzl pleaded guilty to incest and other charges , but denied charges of murder and enslavement -- the most serious charges against him . He pleaded `` Partly guilty '' to multiple charges of rape , but did not elaborate . `` Partly guilty '' is a plea option in Austrian courts . Franz Cutka , a spokesman for the Landesgericht St. Poelten court , said the `` partly guilty '' plea might mean that Fritzl contends he is not guilty of all the individual rape charges or that the violence used was not as severe as rape . Cutka was not in court for the plea and does not speak for the defendant . Fritzl 's attorney was not immediately available to explain what he meant . Fritzl arrived at the courthouse in St. Poelten covering his face with a blue binder to shield himself from reporters , television cameras and photographers and escorted by a phalanx of police officers . Watch Fritzl arrive in court '' Fritzl faces six charges at a closed-door trial in St. Poelten , 45 miles -LRB- 70 km -RRB- east of Amstetten , where Fritzl lived . Cameras were removed from the court The trial is scheduled to last five days , but his attorney Rudolph Mayer said it could be shorter . Fritzl was charged in November with incest and the repeated rape of his daughter , Elisabeth , over a 24-year period . But he was also charged with the murder of one of the children he fathered with her , an infant who died soon after birth . State Prosecutor Gerhard Sedlacek said Michael Fritzl died from lack of medical care . In an opening statement , prosecuting attorney Christiane Burkheiser handed damp-smelling items from the cellar where Elisabeth and her children had lived to jurors to give them an idea of the conditions in which they were allegedly locked up . In all , Fritzl is charged with : murder , involvement in slave trade -LRB- slavery -RRB- , rape , incest , assault and deprivation of liberty , Sedlacek 's office said . He could face a maximum sentence of life in prison if convicted of murder . Mayer said Sunday that Fritzl expected to spend the rest of his life in prison . `` This man obviously led a double life for 24 years . He had a wife and had seven kids with her . And then he had another family with his daughter , fathered another seven children with her , '' said Franz Polzer , a police officer in Amstetten , the town where Fritzl lived , at the time of his arrest . The case first came to light in April 2008 when Elisabeth 's daughter , Kerstin , became seriously ill with convulsions . Elisabeth persuaded her father to allow Kerstin , then 19 , to be taken to a hospital for treatment . Hospital staff became suspicious of the case and alerted police , who discovered the family members in the cellar . Fritzl confessed to police that he raped his daughter , kept her and their children in captivity and burned the body of the dead infant in an oven in the house . Elisabeth told police the infant was one of twins who died a few days after birth . When Elisabeth gained her freedom , she told police her father began sexually abusing her at age 11 . On August 8 , 1984 , she told police , her father enticed her into the basement , where he drugged her , put her in handcuffs and locked her in a room . Fritzl explained Elisabeth 's disappearance in 1984 by saying the girl , who was then 18 , had run away from home . He backed up the story with letters he forced Elisabeth to write . Elisabeth Fritzl and all but three of her children lived in the specially designed cellar beneath her father 's home in Amstetten , Austria , west of Vienna . The other three children lived upstairs with Fritzl and his wife ; Fritzl had left them on his own doorstep , pretending the missing Elisabeth had dropped them off . Under Austrian law , if Fritzl is convicted on several offenses , he will be given the sentence linked to the worst crime . The charges he faces are : • Murder : The infant who died in 1996 died from a lack of medical care , the state prosecutor said . The charge carries a sentence of life in prison . • Involvement in slave trade : From 1984 until 2008 , prosecutors allege , Fritzl held his daughter , Elisabeth , captive in a dungeon , abused her sexually and treated her as if she were his personal property -- in a situation similar to slavery . If he is convicted , the sentence could range from 10 to 20 years in prison . • Rape : Between August 30 , 1984 , and June 30 , 1989 , Fritzl `` regularly sexually abused Elisabeth , '' according to the prosecutor . The sentence could be from five to 15 years in prison . • Incest : Parallel to the rape charge . It carries a sentence of up to one year . • Withdrawal of liberty : Three of the children Fritzl had with Elisabeth were illegally held captive in a dungeon with no daylight or fresh air , according to prosecutors . That charge carries a sentence of one to 10 years . • Assault : Between August 28 , 1984 , and April 26 , 2006 , Fritzl repeatedly threatened Elisabeth and their three children with gas and booby traps as warnings in case they tried to escape , authorities allege . The sentence would range from six months to five years . CNN 's Frederik Pleitgen and Melissa Gray contributed to this report .