Douglas P. Lyle

Ever wonder just how prevalent various crimes are? Or about what you should do if you witness a crime? This Cheat Sheet covers that and more, such as how investigators approach a crime scene and the tools they bring to bear in their search for clues, as well as how the medical examiner or coroner determines the cause, mechanism, and manner of death.

In general, all forms of evidence have class or individual characteristics. Class characteristics are not unique to a particular object but place the particular bit of evidence into a group of objects. Individual characteristics narrow down the evidence to a single, individual source. The type of handgun with which a victim is shot is a class characteristic.

You're probably familiar with the TV series CSI: Crime Scene Investigation and its many spin-off shows. How could you not be? Though they more often than not get the science right, they create an unrealistic picture of what a crime lab looks like, how well equipped it is, and what CSI and lab techs actually do.

Because forensics is such a hot topic these days, millions of viewers are becoming armchair experts on that subject. But is Hollywood reliable? Sometimes yes, sometimes no. The quick death A gun is shot or a knife is thrown and down goes one of the bad guys, perhaps clutching his chest or taking one last dramatic breath, but either way, he's instantly a goner.

The size of a crime scene can vary greatly and the police must be prepared to quickly determine its boundaries. This task is not as easy as it seems. A crime scene may be a single room, an entire house, everything on a property, or even a whole neighborhood. And that's just the primary scene. At a minimum, the crime scene includes The exact spot where the offense took place Areas from which the site can be entered and exited Locations of key pieces of evidence, such as the body in a murder, a safe or cabinet in a burglary, or an entire structure in a suspicious fire A crime scene can be cordoned off using crime-scene tape, barricades, automobiles, or even by police officers standing guard.

For those interested in digging deeper into the science and techniques of forensic science and criminal investigation, here are some excellent resources for further study. The Writers' Forensics Blog This is DP Lyle, MD's blog. Though originally geared toward writers of crime fiction, this blog is followed by forensics industry professionals and those who have an interest in crime and forensic science.

Many criminals attempt to damage, alter, or remove their fingerprints to avoid identification or connection to prints found at a crime scene. From John Dillinger to more "common" criminals, these efforts are usually unsuccessful. Still, if, after leaving prints at a scene, the perpetrator successfully alters or damages his prints, the fingerprint examiner may not be able to make a reliable match.

On April 5, 1994, the body of Kurt Cobain, singer/songwriter for the grunge rock group Nirvana, was found in an over-the-garage apartment at his home. His wife, Courtney Love, was in another state at the time of his death, so he was home alone. Or at least it appeared that way. He was found lying on his back, with a shotgun resting on his chest, and an obvious shotgun blast beneath his chin was the cause of death.