A Danish man accused of bludgeoning a German backpacker to death on a Baltic Sea cruise more than three decades ago was set free by judges in Finland on Wednesday.

Prosecutors accused the 52-year-old, identified in court only as Herman H, of killing Klaus Schelkle, 20, and attempting to murder his girlfriend Bettina Taxis.

The fatal incident took place on the Viking Sally ferry that was travelling from Sweden to Finland in July 1987.

The couple were found with serious head injuries in the ship's sleeping area. Schelke died as he was being airlifted to hospital.

Taxis survived but suffered lifelong injuries.

The man, who was 18 at the time, was arrested last year after new information emerged in one of the longest unresolved cases in Finnish history.

The case against Herman H

Prosecution lawyers claimed the suspect had confessed to committing the crime and wanted the court in Turku to hand him a life sentence, pointing to his apparent knowledge that the murder weapon was a welding hammer.

They said Herman H had told several people that he had "killed and got away with murder."

Defense attorneys rejected that argument, saying their client denied all the charges.

They said Herman H would make such so-called confessions to scare people and test whether they could be trusted or not.

The court agreed. Judges ruled that the prosecution "failed to prove the defendant was the only person with the opportunity and possibility of carrying out the offences".

What damages were paid out?

They ordered the Finnish state to pay the defendant 3,000 euros ($4,791) in compensation.

Judges also said that because the murder weapon had never been recovered it was impossible to establish sufficient proof that Herman H was the author of the crime.

Police never released any information about the hammer.

A further setback for the prosecution was the refusal of a key witness — the defendant's former wife — to give evidence at the trial.

Officers questioned all of the passengers at the time. But travel records were incomplete and there was no DNA or CCTV evidence to assist their enquiries.

The Viking Sally was later renamed the MS Estonia, which sank during a crossing from Estonia to Sweden in 1994, killing 852 people.

jf/aw (AFP, AP, dpa)