Prosecutors have filed homicide charges against a 1969-born Danish man over a crime that occurred on board a Viking Line ferry in 1987.
"I have no reason to believe that the trial wouldn't start as scheduled," said district prosecutor Kai Selander.
Authorities have not remanded the defendant, who lives in Denmark. The trial is set to begin in Southwest Finland district court next May.
Prosecutors said the victims were attacked in their sleep, making the crime especially heinous and cruel.
Twenty-year-old Klaus Schelkle died in the attack while his 22-year-old girlfriend, Bettina Taxis, sustained serious injuries.
Danish boy scouts were the first to discover the victims.
The defendant has denied the charges.
Viking Sally later became MS Estonia, which in 1994 sank off the island of Utö in the Turku archipelago, claiming 852 lives.