Automatic Matching of Scans from Hamby Sets: Friends, False Friends, and Clones

Over the past year, we have had the opportunity to scan several Hamby Sets from different Forensic Labs. Scans from another two Hamby sets are available from the National Ballistics and Toolmarks Research Database. We were also given two clone sets by Prof Hamby.
This gave us at least twelve bullets from each of the barrels and allowed us to turn the tables: Instead of matching bullets to bullets, we can now take a look at how well each of the ten barrels marks and how much variability we see in the scores for each of the barrels.
Using the automatic matching algorithm, we were also able to evaluate the clone bullets in more detail and compare scores from clone to clone and clone to bullet. Results show that clones generally result in lower scores, but are still identified as matches to bullets from the same barrel.