Bournemouth University - Forensics
Measuring Instruments
Bournemouth University - Forensics
Bournemouth University and Forensic Footwear Evidence Case Study
The School of Conservation Sciences, Bournemouth University, is engaged in a wide range of geographical, forensic and archaeological research. In particular Professor Matthew Bennett has been using the Konica Minolta Vi-900 Optical Laser Scanner to record human and animal trace fossils – footprints – from a range of different geological environments around the World.
- Series of footprints left by the same individual wearing four different shoes, two of which are identical but with different degrees of wear
In the forensic context footwear traces come in a variety of different forms from the classic ‘footprint in the flower bed’ to subtle traces left by muddy shoes or blood-stained feet. Although the materials and techniques used in the collection of footwear evidence have become increasingly sophisticated, the basic premise of photographing, casting, or lifting of footwear evidence remains consistent. In the case of three-dimensional impressions within soil, which form the focus of this case study,traditional methods of preservation and analysis involve some form of casting technique. Casting of footwear evidence is not however without some critical challenges and in this case study we demonstrate that the use of the Vi-900 for three-dimensional optical laser scanning provides an alternative approach to the collection, preservation and analysis of footwear evidence. In creating high resolution Digital Elevation Models of prints at the crime scene, using the Konica Minolta Vi-900, the investigator has immediate access to three-dimensional data on footwear impressions which can be stored and accessed electronically and treated in a more quantitative fashion.
- Optical laser scan with photographic render showing detail that can be recorded from a suspects footprint.
We used a series of simulations in the laboratory to demonstrate the technique. A simple sand box was created and filled with soft builder’s sand and maintained at a constant moisture level. Footwear images were captured via a Konica Minolta Vi-900 mounted in horizontal mode on a custom built rig. Data was processed in RapidformTM and exported to ArcGISTM as XYZ data files for some operations.
- Tessellated laser scans of a sand tray showing three footprints. Colour rendered scans showing variations in elevation.
To demonstrate the resolution of the scanner a series of barefoot impressions were made within the sand tray. The image was created by tessellating a series of adjacent scans within RapidformTM and then using the ‘Measure-Contour’ tool to render the surface with a series of coloured isopleths to bring out the anatomical details within the prints. Direct measurement can bemade from the tessellated scan in order to make inferences about gait and foot dimensions. The sand tray was again scanned sequentially along its length and the scans tessellated to create a single image. The sole of each piece of footwear was also scanned. It is possible to not only recognise each piece of footwear in the sand tray but also to distinguish between the two similar items of footwear each of which had different degrees of wear. The latter is essential in linking a suspect wearing a common type of shoe to a particular crime scene and can be as effective as a footprint given that wear patterns tend to be unique to a given individual. The images within this case study truly reflect the accuracy that can be gained by the Konica Minolta Vi-900.