He had made it through four years of denials and appeals, and Robert Heard was finally before a Social Security judge who would decide whether he qualified for disability benefits. Two debilitating strokes had left the 47-year-old electrician with halting speech, an enlarged heart and violent tremors. There was just one final step: A vocational expert hired by the Social Security Administration had to tell the judge if there was any work Heard could still do despite his condition. Heard was stunned as the expert canvassed his computer and announced his findings: He could find work as a nut sorter,...