SHOT THROUGH THE HEART PART II
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 some 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….
Now let’s switch to the other end of the gun, for gunshot residue can also refer to what winds up on the victim. When a gun is fired, not just the bullet comes out of the end of the muzzle. Tiny particles of gunpowder with spew out in an ever-widening circle until they lose momentum and fall to the ground. There will also be a cloud of gray matter (fouling), composed of tiny metal particles, mostly lead, scraped from the sides of the muzzle and the sides of the bullet as they encounter each other. This cloud will only travel up to 6 inches, so if there is a circle of black soot around the bullet hole in the victim’s shirt, you know the killer got up close and personal. If the killer got very close, then the bullet hole may appear to be more of a rip than a hole, a cross-shaped pattern of jagged tears. This is known as a ‘contact’ wound—the muzzle of the gun was pressed against the person and the expanding gases from the muzzle caused the shirt (and, usually, the wound) to more or less explode.
A neater hole with no fouling implies that the muzzle was more than 6 inches away. Flecks of gunpowder may be visible with a stereomicroscope. Gunpowder comes in ball, rod and flake (or disc) shapes, but the most common is flakes, which look like flat discs. They might have holes in them, which increases the surface area for faster burning. Burnt or partially burnt particles of gunpowder can be found on the clothing with a Griess test (also known as a modified Walker test). This is an absurdly simple test which can tell you terribly important things. A piece of treated photographic paper is placed face up, the article of clothing is placed face down, and a piece of gauze soaked in acetic acid is placed on the inside of the clothing. This is heated with an iron and voila, the nitrites in the gunpowder produces orange dots on the photographic paper.
Since the gunpowder spreads out as it moves through the air, the amount and grouping of orange dots tells you something about where the muzzle of the gun was. (Not where the shooter was, just the gun. He might have it close to his body, or fully extended. He might have really long arms, who knows?) If the paper lights up like a Christmas tree, it was fairly close. If there’s only a few sporadic dots, the gun was probably two or three feet away at least. If there’s no dots at all, the gun was probably at least three feet away. If you get the actual gun and the actual ammunition used, a series of test firings can zero in the distance with impressive accuracy.
I’m a big fan of this test, I admit. It doesn’t require a lot of training and in five minutes you can tell that if the killer said they struggled and the gun went off, and there’s no nitrites, then it’s more like that he shot the guy from across the room. If the wife says she shot him by accident, seeing only a shadowy figure fifteen feet down the hallway and there’s a tight grouping of orange dots around the bullet hole, then, well, she’s got some ‘splainin’ to do.
