The trial against the defendant, identified as Daniel H., moved into its second day on Wednesday after the prosecution outlined its evidence in a sensational case that has attracted nationwide attention in Switzerland.
The man, previously arrested for attempting to strangle a woman, lured the girl to his home on March 4th, 2012 by promising her 500 francs ($546) for jewellery photos.
He is alleged to have had sex with the girl before bashing her in the skull with a barbell and slitting her throat with a knife.
“The act was cold-blooded, senseless, ruthless and of incredible brutality,” prosecutor Dominik Aufdenblatten told the court.
The prosecution previously stated Daniel H. had approached around 110 girls and other young women before Trezzini agreed to accompany him.
Daniel H. admits that he committed a “bestial and appalling” act that took place under the influence of drink and drugs and that he now says he regrets.
But one of two specialists called by the prosecution cast doubts on the possibility of reforming what one of them called a “potential serial killer”.
Trezzini’s mother told reporters gathered at the courtroom that she did not believe the defendant’s words and expressed the hope that he is imprisoned for life.
She recalled how the family’s world “collapsed” when the parents first received the news about the death of their daughter.
“There were horror days we spent looking for her,” father Roland Trezzini said, according to a report carried by the Blick newspaper.
Defence lawyers are presenting their side of the case on Wednesday.
Because of the intense media interest in the case, the trial is being held in the municipal hall of Untersiggenthal because the town’s courtroom is too small.