In an important test of legal standards for death penalty cases, the Supreme Court on Thursday overturned the sentence of a Maryland inmate, saying his lawyers had not adequately investigated his history as a victim of childhood abuse.

The court declared in a 7-2 ruling that the performance of Kevin Wiggins’ lawyers in the states’ courts violated the convicted murderer’s Sixth Amendment right to effective assistance of legal counsel.

The court ordered a new sentencing hearing in a decision praised by death penalty opponents and constitutional rights groups.

Because of the court’s action, more death row inmates will be able to push forward with claims that their representation did not meet constitutional standards, said Steven Hawkins, director of National Coalition to Abolish the Death Penalty.