Citizen Police Academy: Week 4

Citizen Police Academy

(Click the photos for a larger view.)

A CPA student prepares plaster to take a mold of a footprint.

To get an impression of a footprint in the mud, a CPA student pours plaster over the footprint.

A CPA student takes a sample of the fake.blood the "suspect" left on the jagged window.

Officer Willie Meyer shows a CPA student how to dust for fingerprints at a mock crime scene.



Week 4


Crime Scene/Evidence Procedures

Mock Crime Scene

Northern Illinois Police Crime Laboratory






Evidence gathering and processing is a business Police Evidence Technicians (ETs) take very seriously, and with good reason. Solid evidence taken from a crime scene can often solve a crime or help garner a successful verdict in court. But gather or process evidence improperly, and a criminal may go free. 

Sgt. Christine Saffell and Officer Willie Meyer opened the world of evidence gathering and processing to CPA students in tonight's session and tried to hammer in the gravity of the responsibility held by ETs. Sgt. Saffell began the class with a discussion of home break-ins. She described a scenario in which a suspect walks around the outside of a house searching for a window in which to enter the home. He finds a window and--Clue #1--leaves his footprint in the mud below the window. He breaks the glass and, as he crawls through, rips his glove--and his skin--on the jagged glass. Clues #2, #3, and #4: fibers from the torn glove, drops of blood on the glass, and a fragment of a handprint.

Sgt. Saffell outlined the types of evidence for which ETs would comb the inside of the house and how they would gather the evidence they found. As an extra bonus, she offered advice one might take to make his or her home less susceptible to a home break-in.

During the second hour, the CPA students found their way across the street to Fire Station #2 where Sgt. Saffell and Officer Meyer had set up a mock crime scene, complete with a footprint in the mud, bloody broken window, soiled T-shirt within the "house," and fingerprints left on the glass. Officer Meyer described the steps an ET follows when taking a plaster mold of a footprint, as well as how blood, fibers, and prints from the broken window would be retrieved and safely stored. As he explained the procedures, students acted as ETs and followed his directions for gathering the evidence.

After our brief, hands-on approach to evidence gathering, we returned to the police station to hear how the evidence just gathered would be processed. Jeff Gurvis, a Crime Lab Technician from the Northern Illinois Police Crime Laboratory, detailed how ETs at the crime lab process evidence. For example, did you know that when drugs are confiscated from someone, the suspect cannot be convicted in court on the drug charge unless it is proven that the substances seized are really drugs? To do that, evidence technicians put the substances through a series of chemical tests to determine what a substance actually is. Fascinating. Next, Jeff described how cases are solved through fingerprinting. He explained that fingerprints are formed in the womb by the flow of fluids, the fetus touching the womb walls, and other factors. Therefore, no two fingerprints can be alike--not even fingerprints of identical twins! He said that the configuration of a fingerprint is so unique that often they are able to make an I.D. off just a portion of a print left at a scene.

Jeff described other methods of evidence processing, such as tracing spent bullets to the guns that fired them, blood spatter evidence, and more. Before we knew it, it was 10:00 p.m., so Jeff called it a night. Next week's class will feature Radar, Gurnee's canine officer. See you then!