Crime Scene Procedures

The purpose of crime scene investigation is to help establish what happened (crime scene reconstruction) and to identify the responsible person. This is done by carefully documenting the conditions at a crime scene and recognizing all relevant physical evidence. The ability to recognize and properly collect physical evidence is oftentimes critical to both solving and prosecuting violent crimes.

The major assignments, as well as corresponding general duties and responsibilities, are set forth as follows:

Team Leader
Photographer and Photographic Log Recorder
Sketch Preparer
Evidence Recorder/Evidence Recovery Personnel
Specialists

Basic Stages in a Search

Approach scene Secure and protect scene
Initiate preliminary survey/determine scene boundaries
Evaluate physical evidence possibilities
Prepare narrative description
Depict scene photographically
Prepare diagram/sketch of scene
Conduct detailed search
Record and collect physical evidence
Conduct final survey
Release crime scene

Assignment: What is Locard’s Exchange Principle?

Trace evidence is based on Locard’s Exchange Principle which contends that every contact, no matter how slight, will leave a trace. The trace is normally caused by objects or substances contacting one another, and leaving a minute sample on the contact surfaces.

The main point is that some apparently foreign object or piece of material has been brought to a crime scene and tracing its origin can assist in an arrest and conviction. Similarly, finding some trace from the victim or crime scene on a suspect can also have a strong impact on a case.

Pre-lab Procedure

The day before the lab, choose a clean shirt, and wear it throughout the day.
Record your movements during the day. Describe the type of location and the people, animals, and activities you encounter.
At the end of the day, seal the shirt in a zip-top bag and bring it into school.

Lab Day Procedure

Clean the laboratory bench top with soap and water to inhibit contamination.
Carefully, remove the shirt from the bag and lay it flat on the bench top.
Using a hand lens and forceps, scan the shirt for any hairs or fibers and remove them using the forceps. Place the hairs and fibers you find inside small envelopes or use a clean sheet of paper to make druggist folds. Take special care around the collar area.
Note any stains or discoloration on the fabric.
Turn the shirt over and repeat this process.
Examine your hair and fibers under the microscope.
Group together hairs or fibers that look the same.
Try to identify each group based on your movements while wearing the shirt.

Questions

Make a chart relating each sample you found on your shirt to one of your activities while wearing the shirt. (If there are some samples that don’t seem to relate to any of your activities, list them with a? beside them.)
Make a hypothesis about how hairs or fibers that don’t seem to relate to your activities could have gotten onto your shirt.

SKETCHING THE SCENE

The Photograph is ordinarily a two-dimensional representation of the scene of the crime and, as such, does not provide accurate information concerning the distance between various points in the scene. The relationship existing between objects present in the scene cannot be clearly understood unless the measured distances are known. Certain objects, moreover, are not visible in a photograph or cannot be clearly identified. A drawing or crime scene sketch is the simplest and most effective way of showing actual measurements and of identifying significant items of evidence in their locations at the scene. Sketches are divided generally into rough sketches and finished drawings.

Rough Sketch. The rough sketch is made by the investigator on the scene. It need not be drawn to scale, but the proportions should be approximated and the appropriate measurements or dimensions shown. The rough sketch may be used as a basis for the finished drawing. No Changes should be made on the original sketch after the investigator has left the scene.

Finished Drawing. The finished drawing is made primarily for courtroom presentation. It is generally based on the rough and drawn to scale by a person skilled in either mechanical or architectural drawing

ASSIGNMENT: Crime Scene Sketching

Generate a finished sketch from the rough sketch attached.
It is necessary to draw the room to scale, meaning that the distance recorded in the rough sketch are the same proportion in the finished sketch. This can easily be accomplished by using graph paper. Remember, the utility of the finished sketch is that it will be entered into evidence and will be presented in court if and when the case goes to trial.
Note the location of any “evidence” you discover. Include those measurements in your sketch.
Indicate the length along each wall, as well as the exact location and size of items like sofas, chairs, and tables. Remember, your sketch will have to provide orientation within the crime scene to other investigators months and years from now-so make it as detailed and as accurate as you can.
Your finished sketch (Google Sketch-Up) should correct any mistakes from the rough draft. This gives you the opportunity to present a clean, clearly arranged diagram of the scene. Be sure to include the address, time, date, (T/P/O) and your name on each and every sketch generated during your investigation. Also include the items of evidence listed on the sketch and indicate the location using the assigned letter (a legend).
On the reverse of your finished sketch, list the physical evidence you believe may be relevant to this investigation and make recommendations about how each should be tested (i.e., sent to DNA laboratory, examined for trace, dusted for fingerprints, collected and taken to the laboratory for tool marks or footprint comparison, etc.). You may want to set it up in a table format.

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