Unless people are dog oriented, they just don't think about scent. Harris says he hasn't found anything yet that he can't get scent from. With concern over drive-by shootings, Harris adds to the list that he had gotten scent from spent shell casings. It's likely that scent can identify a perpetrator, but even if no suspect is developed right away, gauge pads are not expensive. The situation is similar to forgetting to work up a composite likeness of the suspect from a witness, and the erroneous thinking that the most important evidence obtainable from a gun is a fired bullet to be used for ballistic comparison.
Case reports above how scent can be used.
Scent from the scene is tracked by the dog to a suspect, as in the Rhoney case. Scent from a suspect is track by the dog to show how the culprit moved about the scene, as in the Palm Desert burglaries. No matter how you use it, the important thing is to collect the evidence samples in the first place. When you collect evidence, you never know what will become important. The position of mixed brands of cartridges in a revolver cylinder was critical in one case in confirming a suspect's story.