Some hospitals are taking steps to improve safety and reduce their own legal liability from mishaps that lead to higher rates of death, complications, and medical errors that occur when treating patients during thinly staffed off hours. Hospitals are hiring physicians known as nocturnists, who work only night shifts, and some hospitals have begun staffing intensive-care units round-the-clock with critical-care specialists who do double-duty coping with a crisis anywhere in the hospital. And new policies improve communications at the hand-off between the day and night shifts.