Quick note. A Good part of detective work is to know real blood from stage props and stuff, like for example. Blood also has a very distinct smell, that once you know it, you never forget it.
Also note the idea of motive from the type of attack, was this personal? Hate or Obsession?
So things like that might come into play in the whole scheme of things.
CSI uses a lot of Criminology to explain the facts that their forensics find.
Hope that could help you as well.