On December 8, 2007, Damone Jackson was shot while lying in bed at his apartment. Three bullets and three cartridge cases were found on the bed. Jackson was the landlord of his apartment complex. On December 7, 2007, Jackson evicted Rodney Evans from the house, establishing him as a prime suspect. A primer residue kit was collected off Evans and sent to the lab for analysis. The primer residue analysis indicated that the residue consisted of: antimony, barium, and lead. Primer residue is deposited onto the hands in various ways. These include but are not limited to: firing a weapon, handling a weapon, being in close proximity to a weapon being discharged, or coming into contact with an object that has primer residue on it.1 Rodney Evans was a construction worker and claimed that the primer residue came from a powder-actuated tool, also known as a Hilti gun, which was used during his construction work. Hilti is one of the main manufactures of powder-actuated tools. Hilti guns use a primer in which the propellant acts on a piston to drive a fastener into a substrate.
Evans was tried and found not guilty of 2nd degree murder. A key part of the defense was an “expert witness,” another construction worker, who said that the primer residue came from the Hilti gun. The prosecution did not present a rebuttal expert witness.
According to Wolten, et al, there are four compositions that are unique to primer residue and are therefore considered characteristic: (1) lead, antimony, and barium; (2) barium, calcium, and silicon, with a trace of sulfur; (3) barium, calcium, and silicon, with a trace of lead if copper and zinc are absent; and (4) antimony and barium.2 Some other compositions are consistent with gunshot residue but are not unique to it: (1) lead and antimony; (2) lead and barium; (3) lead; (4) barium if sulfur is absent or present only as a trace; and (5) antimony (rare).2
The researchers wanted to prove whether or not all components of primer residue were released when firing a Hilti gun. Even though Evans was found not guilty and can’t be re-tried, this study could turn out to disprove the “Hilti Defense.” The researchers’ hypothesis was that the Hilti gun would not produce all the components of primer residue given that the nail guns are low caliber. The authors’ anticipated results were that only the lead and barium components would be found in the primer residue kit analysis because test fires without the nails did not produce all three primer residue components. The fasteners used were steel, stainless steel, and galvanized steel.
Methods and Materials
An initial test firing was conducted at the Richmond Police Department. To determine the load type, .22, .25, and .27 caliber Hilti guns were fired without fasteners. The Department of Forensic Science Central Lab in Richmond, Virginia, analyzed the load samples. A light, medium, and heavy load were tested and all three resulted in having lead and barium but lacked antimony. The medium load was used for the experiment. The experimental firing took place at Hilti on Broad St. in Richmond, VA. The hands of the person firing the gun were washed prior to test firing to prevent contamination. A tyvek suit and gloves were placed on the person firing the gun to prevent any cross contamination. Ten steel fasteners were fired into a 2x4.