In his maiden opinion for the Supreme Court, new Justice Samuel Alito Jr. said on Monday that states may not prevent criminal defendants from introducing evidence at trial that another person committed the crime.

The unanimous, pro-defendant decision in Holmes v. South Carolina was an unusual debut for Alito, a former U.S. Attorney not known for ruling in favor of the defense when he was a judge on the 3rd U.S. Circuit Court of Appeals. Alito joined the high court Jan. 31, replacing Sandra Day O’Connor.