The case was 0611612 (Gonzalez v United States). Basically, the attorney for the defendant in a criminal trial consented to a federal magistrate judge presiding at jury selection, but after being found guilty the defendant claimed that he should have had to personally give his consent for this to happen. The fifth circuit court disagreed with him, and today the Supreme Court did as well.
Justice Thomas dissented.
For what it's worth, both Thomas and Scalia have the habit of leaning back in their chairs, but of the two only Thomas adds staring at the ceiling :)