A jury’s question, brushed aside as insignificant by the chief justice of the United States, might have made a life-or-death difference, according to a study that challenged the chief justice’s assumptions with mock jurors.

A Cornell University law professor, Stephen Garvey, undertook a study of a jury instruction in the penalty phase of the 1993 trial of Virginia cop-killer Lonnie Weeks Jr., who faces execution on March 16.