A man aged 82 is facing a life sentence in prison in Germany, after going on trial and admitting to a murder that mystified the city of Koblenz for almost 32 years.

Amy Lopez from Texas was last seen alive in September 1994, heading for Ehrenbreitstein Fortress in Koblenz while on a tour of Europe.

Her body was found at the site two hours later.

Hans S, who was 49 at the time, was arrested at a retirement home in the area last February after a DNA trace found on Lopez’s clothing was matched to saliva he had provided during a cold-case investigation.

His full name has not been revealed because of German privacy rules.

Prosecutors believe the attacker met Lopez by chance on the steep path to the fortress.

They accuse Hans S of luring her into a secluded area beneath the fortress, known as the General von Aster room after a 19th-Century Prussian general. He is then alleged to have sexually assaulted and stabbed Lopez nine times.

Prosecutors accuse him of murder and of “base motives to satisfy his sexual urges”.

The court was packed for the first day of the trial on Tuesday, an indication of the notorious nature of the murder in the Koblenz area of western Germany.

The defendant entered the courtroom with a walking frame and, after his defence counsel said he admitted carrying out the crime, the presiding judge asked him to confirm that was the case, and he said “Yes”.

Although an expert psychiatric opinion commissioned by prosecutors considers the suspect to have been criminally responsible at the time of the crime, a final opinion will not come until the end of the trial.

A verdict is expected early next month.

Four years ago a trace of DNA was detected on fragments of skin found on the victim’s trousers because of improved forensic techniques.

However, there had been little movement in the case for decades, until Koblenz authorities set up a special cold-case investigation team last year. There had been repeated appeals to the public and the case was even highlighted last year on a national TV unsolved crime show.

Although several leads emerged from the programme, it was only when police began taking saliva samples from volunteers that they made an arrest at a residential home near Koblenz. Prosecutors spoke of a clear DNA match for one of the traces.

Asked why Hans S had provided a sample, his lawyer told German news agency DPA that the case had “weighed heavily” on him and he had wanted closure.

The suspect had already been convicted of a sexual offence in 1999, but police at the time did not have sufficient DNA evidence to link him to the 1994 killing.