Investigation into the repeatability and precision of casting 3D impressions.

Abstract

The procedure of casting of 3D footwear impressions found at crime scenes has been in place since the early 1900s. For many CSI’s casting is often considered to be the gold standard for recovery, despite little or no research to validate the method in terms of reliability, repeatability and accuracy. In the UK casting has fallen out of favour except in the most important cases due to the time it takes and improvements in conventional forensic photography. It is, however, still widely used in other countries. With the increasing availability of digital alternatives for 3D recovery such as the use of optical laser scanning or SfM photogrammetry it is perhaps timely to consider the potential errors around casting. Using a dataset of 20 casts all created from one flexible silicon mould, two separate assessments are used to examine the variability between each of the casts to determine an estimate of precision.