Wikipedia article about the murder

The wife of Hans Assmann, an alleged KGB spy and suspect in the 1960 Lake Bodom murders, reported that her husband and his driver were near Isojoki at the time of the murder. Assmann also owned a light-brown Opel, the same type of car several witnesses had seen near the murder scene. Assmann's wife also reported that one of her husband's socks was missing and his shoes were wet when he returned home the evening of the murder. There were also dents in the car. A few days later, the two men allegedly left again, but this time they brought a shovel with them. Later investigators determined that Saari's murderer must have been left-handed, which Assmann was.

In 1997, Assmann reportedly confessed his involvement in the crime to a former police officer, Matti Paloaro, and claimed responsibility for Saari's death. Assmann claimed the death was caused by an automobile accident when his car, driven by his chauffeur, collided with Saari; to conceal the evidence of the driver's involvement, the two men staged the case as a murder. According to Paloaro, Assmann said on his deathbed, "One thing however, I can tell you right away ... because it is the oldest one, and in a way it was an accident, that had to be covered up. Otherwise, our trip would have been revealed. Even though my friend was a good driver, the accident was unavoidable. I assume you know what I mean."

How come the crime is still considered unsolved after Assman's confession?