There may be no act of human failing that more fundamentally challenges our society's views about crime, punishment, justice, and mercy. According to statistics compiled by a national childs' safety advocacy group, in about 40 percent of cases, authorities examine the evidence, determine that the child's death was a terrible accident - a mistake of memory that delivers a lifelong sentence of guilt far greater than any a judge or jury could mete out - and file no charges. In the other 60 percent of the cases, parsing essentially identical facts and applying them to essentially identical laws, authorities decide that the negligence was so great and the injury so grievous that it must be called a felony, and it must be aggressively pursued.