Development of double casts for the validation of three-dimensional imaging systems for firearm forensics

Three-dimensional imaging systems for firearm forensics have been developed and are being marketed using promises of increased comparison accuracy and casework efficiency. However, before these systems can be applied to casework routines, the purchasing laboratory must perform a deployment validation. An Academy Standards Board (ASB) standard (063) was published on 3D system validation stating the need for a deployment validation, but no specifics were provided as to how laboratories should conduct such a validation. Designing a deployment validation removes an examiner from casework temporarily, reducing casework output, costs the laboratory time before a new system can be put online to assist in casework, and costs the laboratory money for the ammunition needed to test fire the cartridge cases and bullets that are needed.

A master validation set is urgently needed to reduce the time and cost associated with laboratories performing their own validation studies. A master validation set created using physical cartridge cases and bullets is not able to be sent to multiple laboratories without doing a “round-robin” approach where Laboratory A, upon completion of the validation, sends the cases to Laboratory B, who then forwards the validation to Laboratory C, and so on. This is ineffective in reducing time to validate new systems. The proposed study aims to create a master set of cartridge cases and bullets, and then replicate these physical samples using the double casting process. These double cast replicas can then be sent to any laboratory of interest, and the master set can be replicated any number of times. In practice, this means that forensic laboratories will be able to have a full validation study on-site Day 1 with a new 3D instrument, reducing the amount of time examiners need to be removed from casework and saving the laboratory costs associated with test firing firearms. Furthermore, some laboratories may not have a large enough firearm reference collection with enough replicate model firearms to properly set up such a validation.
Partnership between the Miami-Dade forensic laboratory and the University of Central Oklahoma (UCO) is critical for this project. The Miami-Dade laboratory is currently in the process of validating their own 3D system, providing valuable insight into the validation process. Practicing firearm examiners will be involved in the development of the validation sets, and casework firearms will be utilized in creating all test fired cartridge cases and bullets. UCO will mainly be responsible for initial design of test sets, 3D scanning, double casting, and distribution of double casts to labs. As adoption of 3D technologies is rapidly increasing, now is the perfect time to develop and disseminate a standard set of validation cases and bullets. Dissemination is planned through open-access publication to the Journal of Forensic Sciences, presentations at both the American Academy of Forensic Sciences (AAFS) and Association of Firearm and Toolmark Examiners (AFTE) national conferences, and advertisements placed in welcome packets for all attendees at the AFTE conference. CA/NCF