LINCOLN, Neb. (AP) — A Nebraska man serving life in prison for killing his 12-year-old sister when he was 14 will get a new sentence.

The Nebraska Supreme Court ordered the resentencing for Sydney L. Thieszen in a ruling issued Friday.

Thieszen had filed a motion for post-conviction relief in 2013 in light of a U.S. Supreme Court ruling that declared mandatory life-without-parole sentences unconstitutional for juvenile offenders. A district court judge granted Thieszen’s motion, and prosecutors appealed.

Thieszen was convicted in 1988 of killing his sister, Sacha Thieszen, at their home near Henderson. Prosecutors say Thieszen killed his sister because he was afraid she would tell police he was running away from home.