Currently, the availability of optical topography instruments – 3D technologies, have become more accessible for forensic laboratories. Due to the precision and accuracy of these instruments, the scientific community of forensic Firearms/Toolmarks (F/T) identification has begun to investigate their utility in forensic F/T casework.


To provide guidance and recommendations to the F/T community in instrument assessment and Virtual Comparison Microscopy (VCM).

Creating standards for the F/T community to establish acceptable measuring practices, methodology/Standard Operating Procedures (SOPs), and quality assurance protocols that can be utilized to access a laboratory’s compliance during accreditation.


The TWG3D2T membership is comprised of state, local, private, federal, and international forensic firearms and toolmark examiners along with academia, research metrologists, and legal professionals.

Public Comments

The TWG3D2T is seeking public comments on a draft document titled “Best practice guide for the calibration and quality control of 3D surface topography measurement instruments used for Virtual Comparison Microscopy (VCM) of toolmarks”.

Documents for Public Comment

Please submit your public comments to Alan Zheng ( by November 30, 2023 using the form included in the downloaded package.