In this case, a gunsmith was able to examine the revolver found on Jenning's person right after the crime was committed. Prior to examining officers took note of the smell of burned powder and fresh smoke at the scene. After retrieving the revolver, they then noticed burned powder in two chambers of the cylinder of the gun. Also found at the scene was two lead slugs, three unfired cartridges, and the dead body of Mr. Hiller who had been shot twice, through his heart and lungs. Detectives then went to chemical examination of the revolver and found that two chambers had contained burned particles of powder, showing that the gun had very recently been fired. This is done by collecting samples from the inside of the gun chambers and using a chemical to detect whether or not nitrates are present. If they are present, the gunpowder has been burned likely from the discharging of a bullet. The notion that two bullets had been fired was later corroborated by the testimony of a gunsmith who agreed upon examination that there were two chambers containing burned particles of powder.
As for the gun, detectives were able to track the revolver back to a pawn shop as Jennings had been forced to pawn it due to financial issues. The day before the murder however, he bought it back and then used this gun to shoot Mr. Hiller.
All of this information, the smell of the freshly burned gunpowder, the cartridges found at the scene, the chemical examination of the gunpowder, and the testimony of the gunsmith was enough in the eyes of the law to link that gun to Jennings and eventually him to the scene.
Technique Highlighted:
Firearm examination
Techniques Mentioned:
Crime scene investigation
Post mortem examination
Forensic chemistry