The PI's Role in the Crime Scene

The PI’s Role in the Crime Scene

PIs rarely deal with a crime scene, except under certain circumstances, and usually only after the police have abandoned it. The best action if you’re the first to arrive at a crime scene is to touch nothing and call the police. However, should someone be injured and need help, or be in imminent danger of injury or death, you may be forced to enter the scene. In this case you need to know something about crime scene procedure and evidence handling.

Law enforcement officers follow a standard procedure for crime scene handling and processing. The most important rule in this procedure is protection of the scene. Only a few circumstances allow for anyone to enter a crime scene before it’s been processed. The first, and most important, of these circumstances is threat of injury or death to someone inside.

Another circumstance in which police enter a crime scene before it’s processed is if evidence could possibly be destroyed. For example, if drugs are known to be inside, there’s a chance they will be flushed. In this case, police usually enter and prevent this destruction. Most officers advise against the PI attempting to do the same, however. The Private Investigator should only preserve the scene until police arrive.

Investigators approach a crime scene using different methods of collecting evidence. Many of these methods are similar to methods used for searches. For example, some begin collecting evidence at the entrance and work in a pattern toward the exit. Some work in a spiral from the center (or the body if there is one) and work toward the outer edge, and some employ a grid pattern. No matter which method you prefer, be sure that you use one.

In years past, it was procedure in many departments for evidence to be stored in plastics — plastic containers and plastic bags. A good deal of crucial material was rendered useless by sitting in plastics, sometimes for years. It’s now known that paper and metal are the preferred storage materials for evidence. Blood drawn from suspects is placed in vials with different colors.

The scientific examination of this type of evidence falls under the heading of forensics. The two major branches of forensics are Criminalistics and Forensic Medicine. Those trained in these branches are responsible for turning physical clues into evidence. The following list shows what each branch is responsible for examining:

 

Criminalistics Examines:

 Wet Chemistry

 Instrumental Chemistry

 Firearms and Tool Marks

 Photography

 Fingerprints

 Lie Detection

 Questioned Documents

 Voice Spectroscopy

 

Forensic Medicine Examines:

 Pathology

 Serology

 Toxicology

 Odontology

 Psychiatry

Evidence is the backbone of all investigations. However, its efficacy lies in the manner in which it’s handled, collected, stored and processed — all human functions. As human functions, the processing of evidence is subject to mistakes. For instance, mistakes caused by lack of knowledge or training, sloppy handling, lack of adequate personnel, and — while rare — intentional alteration or destruction, can cause evidence to be suspect. In other words, evidence is only as reliable as the people who collect, document, process, and store it.