The boy is said to have carried a firearm and said he used it to kill the 21-year-old man.
He was arrested and on Monday he was arrested, but not on suspicion of murder but for aggravated weapon crime and aggravated protection of a criminal.
The convicted 24-year-old has always denied any wrongdoing.
He appealed the district court ruling but was not heard in the Court of Appeal.
Now he hopes the Supreme Court will take up the case.
SVT is looking for the prosecutor and lawyer.