Judy Clarke, the public defender for the man charged in the Tucson shooting, Jared L. Loughner, has made motions on his behalf and entered a plea for him of not guilty. But one of her most essential acts of lawyering came when she patted Mr. Loughner on the back in court last month, leaned in close and whispered in his ear.

For the small cadre of lawyers specializing in federal death penalty cases, getting the defendant to trust them, or just to grudgingly accept them, can be half the battle. That is especially true when mental illness is a factor, as it may be in the case of Mr. Loughner, a troubled young man accused of opening fire on a crowd on Jan. 8 in an attempt to kill Representative Gabrielle Giffords.