And more importantly, why top investigators using the most sophisticated techniques can work for six months and move only inches closer to finding a cause.

CNN: Six months later, still no answer to TWA Flight 800 mystery

Law enforcement has also become more sophisticated in dealing with child-abuse cases, including refining techniques for interviewing children and using social media to determine whether suspects have established contacts with alleged abuse victims, said Scott Burns, executive director of the National District Attorneys Association.

WSJ: Penn State Case Underscores How Society Deals With Sexual Assault