Forensic biology deals with the identification of blood and other body tissues left at a scene. It has a particular value because, although its primary purpose is to answer the question WHO, its very presence out of the body of the donor carries with it information about WHAT took place (see box below). A bloodstain on broken glass at the point of entry of a break-in creates a nexus between the offence and the person who committed it. Semen in a vaginal swab creates a nexus between the act of intercourse and the male involved. Even without the results of typing tests, as we saw in Chapter 4, the physical pattern of bloodstains can yield information about the manner in which they were deposited. A forceful event, such as running through a pool of shed blood, beating with a club, or a bullet entry, will produce spatters, the size of which becomes smaller as the energy of the event increases. Such spatters contrast with the smears produced by rubbing against shed blood.