Crime Scene Evidence-Convictions are Rare Without Physical Evidence From the Scene

How Crime Scene Evidence Can Make Your Case

By: Don Penven, Tech Support Group

Sensational homicides are populating the National news of late, and crime scene evidence seems to play a key part in many courtroom decisions. Numerous TV “Cop Shows” draw bigger and bigger audiences as the viewing public develops an insatiable appetite for the "blood and guts” of crime scene investigation. 

Crime scene investigation (CSI) includes some basic methods that include forensic applications, photography, chemistry, physics, mathematics and just plain common sense. “How to Become a CSI” is a fast-growing industry among institutes of higher learning offering on-line diplomas and degrees in the discipline. 

One fact is certain: No two crime scenes are very much alike.

 Crime scene investigation must follow an orderly protocol—otherwise physical evidence may be misunderstood, mishandled, or missed altogether. The basics steps taught to crime scene investigators

by many educational sources include, but are not limited to the following steps:

1. Protect Life and Property. The first responding officer(s) must take the steps necessary to protect life and property. First aid is rendered to the injured and aid in the form of emergency medical teams, crash-rescue units, fire departments and backup officers are summoned.
2. Secure the Scene. Officers must take steps to prevent damage to, or disruption (contamination) of the scene. Many experts in this field state that more harm is inflicted on crime scenes by the presence of law enforcement officers than from any other source. The first officers on the scene must make a quick determination of what constitutes the boundaries of the scene, and will then take steps to protect this area. This is where the inevitable “Yellow Crime Scene Tape” is introduced into the crime scene. Sentries must be placed at all possible points of entry and access will be denied to all not having a legitimate reason for entering the area.
3. Brief the Investigators. Except in very small law enforcement agencies—where the first responders may also wear the hats of crime scene investigators, the first responders will brief those on hand who will assume control of the scene and perform evidence search and collection. This briefing includes any observations made by initial officers and will relay statements made by by-standers, witnesses and victims.
4. 4.       Conduct a Walk-Thru of the Crime Scene. The walk-thru is a time spent making visual observations throughout the scene. Physical evidence can be in plain sight (weapons, spent-shell casings, blood, impression evidence (hand and footprints), etc. The investigator will make notes as potential crime scene evidence is revealed. The walk-thru skirts the perimeter of the areas where obvious physical evidence resides. All the while, the investigator is conscious of the fact that a great deal of evidence may be present that is not in plain view or is invisible in nature. Thus he must avoid walking through areas that may harbor footprints in dust, weak or invisible bloodstains or blood spatter and latent fingerprints. 
5. 5.       Recording the Crime Scene. Recording the scene most often begins with CSIs preparing a rough sketch of the area. Locations of furniture and other building contents are included as well as apparent items potentially useful as crime scene evidence. Outdoor scenes present different challenges so nearby vegetation, trees and similar fixed and moveable objects are sketched. Next comes photography. Overall, wide-angle photos record the scene prior to any efforts to locate physical evidence. Medium distance photos follow that show relative positions of evidential items with regard to each other, and then close-ups record specific items. Many agencies also use video to supplement still photographs. As far as human nature is involved, a jury’s rapt attention is often stronger when videos are used to depict the scene. Video provides a sense of actually being at the scene for jurors.
6. Processing the Scene for Physical Evidence. This is the nitty-gritty phase of the investigation. Often, specialists skilled in locating and recovering dust impressions are joined by latent fingerprint technicians who will ply their expertise. In violent crime scenes, a blood spatter analyst will go to work.
7. Collecting the Physical Evidence. It is one thing to locate potential evidence, and it is another to gain the usefulness this evidence may possess. Collecting techniques may include an electrostatic dust print lifting system, superglue fuming of various items in order to reveal invisible latent fingerprints, and there is also a mix of physics and geometry when analyzing and recording blood spatter.
8. Packaging and Transporting Crime Scene Evidence. Much of the evidence collected at a crime scene is very fragile in nature. This evidence may be damaged by handling and the packaging method, and it may deteriorate or “spoil” due to improper storage. Physiological fluids, and their potential for providing DNA profiles, are especially fragile and easily susceptible to damage or deterioration. 

While some TV shows run through all of the above steps in just 45 minutes or so, it is apparent that investigating a crime scene can take many hours or even several days from start to finish.

 

The National Institute of Justice has performed in-depth research into the “CSI Effect.” This is based on the premise that juries are being conditioned to expect to see the very same techniques used by TV actors to be employed by the real-life cadre of CSIs. What the general public expects to see are scientific principles and equipment resulting in “Slam-Dunk” prosecutions, while failing to comprehend that many of the techniques depicted on TV require extensive, virtually unlimited budgets to accomplish. See The NIJ video.

 Most law enforcement CSIs are adapting to the budget crunch, and they are still able to bring the guilty to justice through their dedication and perseverance—despite the lack of sufficient funding.

 Many law enforcement agencies have been forced to limit training and are coming to recognize that a great deal of specific crime scene training is available to them at no cost. The CSI Tech Blog offers specific training in Crime Scene Evidence disciplines, and it is a trusted source for learning the many techniques and procedures needed by today’s crime scene teams. 

To receive Email alerts when new posts are made to this blog: Sign Up For Alerts Here