> If a person committed a crime, they should be able to give details that only the criminal would know, or point in the direction of physical evidence.

Yes! And Bergwall's testimony was often wrong. He guessed for example what was the weapon he must have used. But when he was wrong, he got to "think harder", make another guess, and over time (months or years) he could piece together hints from his interrogators and eventually come up with a somewhat "correct" story vs what secret evidence the police knew. Such as if murderer was using a blunt weapon in the head vs a knife in the abdomen.

It is surreal to read about it.