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SHOT THROUGH THE HEART, PART II: Gunshot Residue

© Elizabeth Becka Lansky

In last month's column we had an introduction to gunshot residue using Atomic Absorption and reasons why the pros and cons of GSR analysis are hotly contested. I ran past my word count limit so had to save the rest of the story:

Most labs currently use an SEM, a scanning electron microscope. The suspect's hands are dabbed with a small 'post', which has a short cylinder with double-sided tape on the bottom of it. The tape is touched to the victim's hands-one set for the 'web' area of each hand (the loose skin between index finger and thumb, extending a little onto the back of the hand), and one set for the palm. Then, the stubs are analyzed by the SEM.

This high powered instrument can not only analyze the tiny GSR particles, it can 'see' them. Sphere-shaped particles combined of barium, antimony and lead are indicative of GSR because the firing of a gun produces temperatures into the thousands of degrees Fahrenheit. Any liquid (or molten metal) moving through the air forms a sphere (a shape with the least amount of surface area). Therefore, a sphere shape indicates the presence of extremely high temperatures during the formation of that particle. When SEM first came out, it was touted as 'proving that someone has fired a gun'. At least that's what the manufacturers told us. Today, however, almost any examiner would state that, similar to AA, the presence of GSR simply indicates that the person was in the vicinity when a gun was fired, or handled a gun which had been fired.

Swabs can't be used in the SEM and stubs can't be used for AA. I often had officers show up at the lab with an SEM kit when we were still doing AA. Or I had officers seek me out because the state lab had gone to SEM and they only had AA kits.

Some labs today are going to EDX, Energy Dispersive X-Ray. More and more sophisticated tests will be developed, of course, but will they ever be able to PROVE that someone fired a gun? These are some of the issues your characters can wrestle with.

Some labs may have discontinued GSR completely. Some labs will only do the analysis for suspects, sometimes only for suspects when there's a reasonable chance for prosecution. Often they will not analyze the kits of victims and witnesses, though they may be collected just in case. At my lab (a coroner's office) we tested everyone, victims, suspects, and accident victims. Of course, this was a great deal of work with many times did not produce any useful information. A GSR analyst character could have a lot of conflicts with other people--lawyers looking for proof, supervisors looking for accuracy, administrators looking to save money.