Defining CT resolution requirements for ballistic forensic evidence

  • Hannah Smith (Speaker)
  • Tawfik, A. (Contributor to Paper or Presentation)
  • Addinall, K. (Contributor to Paper or Presentation)
  • Blunt, L. (Contributor to Paper or Presentation)

Activity: Talk or presentation typesOral presentation

Description

The increase in use and availability of modified and converted firearms in the UK has become a growing threat to the public and a challenge to law enforcement. Within this context there is a need to identify conversions and link this back to the modification tool as well as identifying links to individual criminal acts.
The use of XCT within forensic applications has grown exponentially in recent years from its use in post-mortems to examining crime scene evidence in-situ. It offers a non-destructive means of testing, which is crucial for the preservation of forensic evidence.
In this study a machined artefact and an example of a modified firearm barrel are comparatively scanned using a Nikon XTH 225 and a Nikon 225 MCT. Scans were acquired from both artefacts with identical scan parameters, datasets were then reconstructed using the local iterative surface determination method. The resulting surface data features were then compared across datasets looking at tool marks in the 10-100 µm range.
Metrology-based CT offers increased accuracy and resolution due to the metrology frame principle and often a comparatively smaller voxel size, however this results in substantially larger file size, requiring higher computational power and longer scan times when compared to more standard industrial CT.
In forensic applications, this can be advantageous but in cases where multiple artefacts are under investigation the increased scan time and file sizes may not be required in favour of reduced scan times and more accessible data. It is therefore crucial that there is a developed understanding of the required scale of interest of the resolution needed to detect often macro scale evidence of
modification.
This study discusses the scale of resolution required for different forensic firearms analyses and make recommendations on minimum requirements for CT data and analysis for robust prosecution and presentation of such evidence.
Period15 Jun 2022
Event title6th Dimensional X-ray Computed Tomography Conference
Event typeConference
Conference number6
LocationManchester, United Kingdom
Degree of RecognitionInternational