The Swede was arrested last year in Germany after a tip from Swedish police.
According to the German prosecutor's office, the Swede, who was 17 at the time of his arrest, had offered his services as a contract killer on social media and was recruited to shoot someone to death.
He traveled to Germany at the end of September and was given, among other things, a firearm, ammunition, and a picture of the intended victim, but was arrested before he could carry out the murder.
Since the Swede was not of legal age at the time of the crime, the case is being handled as a juvenile case and the main hearing is being held behind closed doors, the court in Cologne announced.
Corrected: In a previous version, the wrong day of the week was stated for when the trial begins.
