Most murders aren’t that difficult to solve. The husband did it. The wife did it. The boyfriend did it, or the ex-boyfriend did. The crimes fit a pattern, the motives are generally clear.Of course, there are always a handful of cases that don’t fit the template, where the killer is a stranger or the reason for the killing is bizarre. It’s fair to say, however, that nowadays the authorities usually have something to go on. Thanks in part to advances such as DNA technology, the police are seldom baffled anymore.Mortuary photo of the unknown man found dead on Somerton Beach,...