Thomas N., whose surname wasn't released because of privacy rules, went on trial on Tuesday in northern Switzerland charged with murder in the death of a 48-year-old woman, her 13- and 19-year-old sons, and the older teen's 21-year-old girlfriend in December 2015.
Prosecutors in the northern canton (state) of Aargau also accuse the 34-year-old Swiss defendant of extortion, kidnapping, hostage taking, raping the 13-year-old boy, arson and possessing thousands of pictures and videos showing child sex abuse.
Fingerprints and DNA tied the suspect to the scene of the crime in Rupperswil, about 30 kilometers (19 miles) west of Zurich, and prosecutors said at the time that he confessed under questioning. They also said he had no previous convictions or connections to the victims.
The trial is being held in the neighboring town of Schafisheim, and is expected to last until Friday.
Swiss public broadcaster SRF reported that the defendant, during Tuesday's proceedings, said he wanted to one day look after his mother, and was hoping to start a distance-learning course in economics in prison.
"My goal is to someday be back in society and re-socialized," he was quoted as saying.
Swiss daily Tages-Anzeiger reported that the suspect envisaged himself in the distant future seated at a fireplace with a dog at his side.
Prosecutors believe the suspect acted out of financial and sexual motives in the killing of 48-year-old Carla Schauer and the three younger victims.
According to investigators, he tricked his way into the Schauers' home, and made the mother bind and gag the other victims before forcing her to withdraw about $11,000, police captain Markus Gisin said at the time.
After she returned, the suspect tied her up, raped the younger son, killed all four by cutting their throats and set fire to the house, Gisin said.
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