compared with the crime scene exhibits. “As the comparison work in this specific case [was done] using conventional microscopes,” it “was very complicated and time-consuming”; up to 3 firearms examiners at a time worked continuously on the comparisons. Ultimately, test-fired casings from the 3,704th pistol in sequence matched the casings from the second and third murders; this led investigators to an officer in Stuttgart who was ultimately found dead in southern Italy, having also murdered his wife and sons. Grooß concluded that the experience was strong testament to “the individuality of marks on fired bullets and cartridge cases”: that the German examiners were able to observe “marks … which left no doubt that they were identical to those observed on the evidence ammunition,” against a backdrop of “approximately 4000 pistols of the same manufacturer, same model, approximately the same age and same degree of wear.” Apparently, the comparisons with test-fired exhibits were halted with the positive result on the 3,704th pistol, even though the linkage to the casings from the first murder was unclear.
Even when the officer’s pistol was recovered and test fired with a variety of ammunition brands, no casing could be generated that matched the evidence from the first murder. It was originally suspected that the pistol “got a new blue finish” (a refurbishing process that may affect the marks left by the gun) at a time between the first and second murder, which might explain the differences. However, “a more careful examination showed that the pistol had been blued in the period between the second and third murder” (why this did not impede the ability to match the second and third crimes is left unspecified). It was also speculated that the officer might have deliberately planted a different casing at the first crime scene to mislead detectives.