Imagine you are a park ranger on Trail Ridge Road and you come across this strange mark on a roadway. You look around but see nothing unusual. What would you make of the mark and does it give you an idea of what to do next?

I guess I need to make these a little tougher because you all did really well. The mark was produced by a spinning vehicle tire on it’s side (during a roll over). It is what I would loosely call “impression” evidence. I like this photograph for a couple of reasons. First it forces the young CSI to consider associations. In this case if a student were stuck I would simply begin by asking what kinds of “circular” objects could be found on roadways? This is a very simple and common problem solving tactic in crime scene investigation and reconstruction. We have to do this type of analysis in bloodstain pattern analysis all the time. Consider a “pointy” shaped object leaving a bloody outline on a bed sheet following a stabbing. What kinds of “pointy” things might you find associated with a stabbing? If you said “a knife” you’d be right. Of course there could be a lot of things that could fit that broad description but you get the point. It won’t be a baseball bat right?

So, continuing with this tire photo. The next thing this image forces a student to do is to think of crime scene events three dimensionally. Most of the time cars drive upright (on all four wheels) but not always. When don’t they? Accidents. So if this is an accident on a high mountain road what might you be looking for? Perhaps a vehicle off the side of the road right? In the mountains that may be several hundred feet down a mountain side.  Now in reality this mark was found in a city roll over accident, but the investigative process is the same. The last thing I like to use photos like this for is to reinforce that we need more of the picture before we draw any hard conclusions. The same is true in writing. Sometimes as authors we over-simplify our scenes and the evidence. The evidence and the scene makes sense to us because we wrote the scene. But the reader may be coming at it from an entirely different direction. Suddenly your “ah-ha” evidence can be interpreted another way. So, when possible, run some of your evidence discovery scenes past another writer or friend and see if they come to the same conclusion as your characters did.

Next month I promise to give you a more challenging photo that deals with bloodstain pattern analysis and sequencing events. So if you want to get a leg up on your fellow readers take a look at some of my past postings on bloodstain analysis. Thanks to all of you for taking the time to share your thoughts and opinions for this series!