by Nancy Lewis

About the author: Nancy Lewis is a staff writer for the Washington Post.

Even today, six years later, D.C. police Sgt. Bruce Feirson recalls every detail of the case of Chaulette Willis. The call that hot August afternoon came for an address in Southeast Washington that he knew well—a crack house and heroin shooting gallery. When he and paramedics arrived, they found not an adult drug victim but a tiny 4-month-old girl.

She was dirty and reeked of an awful odor, police and medical records show. The skin beneath her unchanged diaper was raw, ulcerated, rotting. The stench in the basement apartment was almost overwhelming. Doctors found two pounds of feces in the diaper of the 10-pound baby.

Chaulette was dead on arrival at the hospital; in fact, she may have been...