- Plume Study Video Sample

A Study of Plume Concentrations from the Discharge of Weapons Commonly used in the United States

By A.J. Schwoeble, W. H. Powers, Sr., RJ Lee Group, Inc.

As suggested by Dennis Ward, FBI, Washington, D.C., the authors visited several law enforcement agencies and crime labs around the U.S. to gain knowledge and information first hand on the sampling technology and analytical techniques utilized by experts in the field related to gunshot residue (GSR). 

A review of sampling protocols practiced by various agencies in the United States prompted the present ongoing study of plume concentrations from the discharge of hand guns, rifles and shotguns. The overall objective is to show the areas with the greatest potential for the collection of GSR under normal firing conditions. All test firings were recorded with a high-speed motion analyzer at 500 frames per second. A new glove was used for each test firing, removed immediately and bagged for particulate sample collection. The particulate will be examined by computer controlled scanning electron microscopy (CCSEM) in the third phase of this program, which is described later in this article.

Summary of Results

Smaller-caliber semi-automatic handguns with high or forward cartridge ejection have plume concentrations toward the front of the fingers – in some instances, heavier than web and wrist areas. In most cases, the plume tends to follow the direction of cartridge ejection. Larger-caliber revolvers have a widespread plume as opposed to the more compact plume of larger-caliber semi-automatic weapons with ejection ports.

The most consistent area of plume concentration for rifles and shotguns is the crook of the support arm; however, blow-back or drift of the original plume formation is toward the chest, shoulder, face and hair with heavy concentrations for some weapons and light in others. Again, cartridge ejection is a factor in many of these weapons.

A thirty-one minute videotape was produced from the test firings which shows slow motion plume development for each weapon. The distribution of potential GSR concentrations from these tests may indicate larger areas to be sampled than present sampling protocols require.

This study is part of a three-phase program initiated through the cooperation and feedback from experts directly concerned with trace evidence, not only related to GSR, but in several other areas that are affected by economical and caseload priorities. An effort was made to include the most common weapons used in the U.S. The videotape was first shown at the 46th Annual Meeting of the American Academy of Forensic Sciences, February 14-19, 1994, in San Antonio, Texas, where suggestions were made for other handgun types to be studied in this manner.

The authors continue the production of an atlas of plume concentration for as many weapons as are made available.  Phase II deals with improvements in sampling technology and the advancements made in the collection of GSR over large areas of skin, clothing and other material surfaces.

Phase III provides for further development of an affordable scanning electron microscope system with applications that yield rapid, multiple GSR analyses with features that provide for unattended automated analysis with electronic relocation of potential GSR particles (within 10 seconds). A Personal SEM® microscope (a registered trademark of ASPEX Corporation) with the GSR application is presently being used at RJ Lee Group to analyze samples submitted by law enforcement agencies. Interest in this program, thus far, has been encouraging and any suggestions or further input from the forensic community would be greatly appreciated.