Can a State Supreme Court overrule their own prior decision?

Yes, they can.

However, if the decision involves a question of federal or constitutional law and the case is petitioned to the US Supreme Court for a writ of certiorari, and if the U.S. Supreme Court grants certiorari, and if the U.S. Supreme Court rules differently from the state supreme court, the state is bound by the U.S. Supreme Court decision under the doctrine of Stare decisis, which is abbreviated from a Latin phrase that means "let the decision stand."