BERLIN — An 81-year-old man admitted to sexually assaulting and killing an American tourist in Germany more than 30 years ago at the opening of his trial on Tuesday, German news agency dpa reported.

The defendant, whose name was not given in line with German privacy rules, admitted to killing 24-year-old Amy Lopez in 1994 in the western German city of Koblenz, the news agency reported.

Prosecutors accused him of “killing a person in a treacherous manner and for base motives in order to satisfy his sexual urges.”

The defense lawyer, Volker Klein, said during the session in the Koblenz district court that the defendant admitted fully to the crime. When the presiding judge, Rupert Stehlin, asked the defendant if that was true, the 81-year-old nodded and said “yes.”

The crime took place Sept. 26, 1994, when Amy Lopez was visiting Koblenz as a tourist.

The prosecution accuses the man, who was 49 years old at the time, of luring her under false pretenses into a secluded room of the Ehrenbreitstein Fortress in Koblenz, where he then allegedly handcuffed her, sexually assaulted her and killed her with nine knife wounds to the chest area.

The suspect allegedly also strangled Lopez with a belt and struck her on the left side of her head with a rock when she tried to defend herself and shouted, dpa reported.

Shortly afterward, children playing nearby found Lopez’s body.

The cold case remained unsolved for decades until investigators analyzed old DNA traces using new methods, ultimately leading to a breakthrough. DNA found on the victim’s waistband and thigh were eventually linked to the man, dpa reported.

The man was arrested in late February at a nursing home in the Koblenz area and has been in pretrial detention since.

A total of eight trial days have been scheduled and a verdict is expected in September.