LJWorld.com weblogs Dispatches from the Academy
Day 6: At the scene of the crime
Journal-World reporters Shaun Hittle and Ian Cummings are attending the Lawrence Police Department's 2013 Citizens' Academy twice per week for the next month. On Wednesdays and Fridays, they'll highlight a few things they learned from the night before.
Crime scene investigation is not as easy as it looks on television.
Just taking your own fingerprint off of an aluminum can, as we learned in an exercise on Day 6 of Citizens' Police Academy, can be infuriatingly difficult. The tape sticks to all the wrong edges, the black powder gets everywhere, and you may end up with nothing but a smudgy blob. That doesn't happen to David Caruso on "CSI: Miami."
But, as Lawrence detectives Randy Glidewell and David Axman showed us, that's only the beginning of how messy real-life police work can be. At any given crime scene, investigators can expect to deal with blood spatter, teeth marks, bodily fluids, bad fingerprints and huge piles of dead flies. Our hands-on exercises Thursday night were thankfully limited to more routine types of evidence, and some of the more disgusting photos we looked at are not included here.
We did get our hands dirty, a little, in the aforementioned fingerprinting. The study of footprints provided other work, as we tried taking evidence-grade photographs from four angles and made casts of the prints with a mixture of dental stone and water.
The whole practice of forensic investigation, as we learned, is based on Locard's Exchange Principle, which says that a perpetrator of a crime always carries away traces of the victim. The opposite is also true, that victims take away traces of the perpetrator.
That principle leads investigators to examine all kinds of gory material. When criminals try to clean the blood from a crime scene, detectives can use a chemical called luminol, or Bluestar, to make it appear in the dark. They will use ultraviolet light to find, and run DNA tests on, semen left on a bed sheet. They will study the life cycle of houseflies to interpret the piles of maggots and the swarming flies around a man who's been hanging in an attic for 10 hot summer days.
Some perpetrators leave more traces than others. Because fingerprints are made in part by oils on the skin, which are controlled by hormones, children don't normally leave behind visible fingerprints. A nervous adult criminal, on the other hand, wiping off his sweaty forehead before touching things, may leave the best prints of all.
To preserve the more difficult fingerprints, investigators will sometimes coat them in a mist of vaporized Super Glue. The glue holds oils and amino acids in place to allow investigators to make several attempts at pulling the print without destroying it.
The department's mobile crime scene investigation truck has a Super Glue machine designed just for that purpose, and we had the chance to inspect it ourselves.
In my own exercise with fingerprinting, I could have used the help of that machine. After brushing on too much black power and smoothing tape over irregular corners, I pulled the tape off and squinted at my own badly-rendered fingerprint. I doubted I could convict myself. It was some consolation to learn that fingerprints only successfully identify suspects about 6 percent of the time.
Walking out of Thursday night's class, we could see Locard's Principle at work among us. We took away with us, from Day 6, ink-stained thumbs and a new understanding of forensic science. We left behind shoe prints in slowly-drying plaster casts, which we will examine when we return Tuesday.
In the meantime I noted the titles of some important texts on crime scene investigation that we saw in class, so I will have some homework to do over the weekend.
To see Shaun Hittle's Day 5 post, The murder of Onzie Branch, click here.