A judge has sentenced a southwest Missouri teenager convicted in his younger stepsister's death to 30 years in prison.

Levi Elliott was 15 when he was accused of fatally shooting 12-year-old Sierra Elliott at their Polk County home west of Bolivar in March 2012 while his father and stepmother were away.

Elliott was brought to trial as an adult. In addition to the second-degree murder charge, a jury also found him guilty of armed criminal action and tampering with a vehicle in October.

The Springfield News-Leader reports a Polk County circuit judge sentenced the now 17-year-old Elliott on Wednesday. A prosecutor says Elliott must serve 20 years in prison before he'll be eligible for parole.

iStockphoto