Chemical enhancement of footwear impressions in blood on fabric – Part 1: Protein stains

Abstract

A range of protein stains were utilised for the enhancement of footwear impressions on a variety of fabric types of different colours with blood as a contaminant. A semi-automated stamping device was used to deliver test impressions at a set force to minimise the variability between impressions; multiple impressions were produced and enhanced by each reagent to determine the repeatability of the enhancement. Results indicated that while most protein stains used in this study successfully enhanced impressions in blood on light coloured fabrics, background staining caused interference on natural fabrics. Enhancement on dark coloured fabrics was only achieved using fluorescent protein stains, as non-fluorescent protein stains provided poor contrast. A further comparison was performed with commercially available protein staining solutions and solutions prepared within the laboratory from the appropriate chemicals. Both solutions performed equally well, though it is recommended to use freshly prepared solutions whenever possible.

Chemical enhancement of footwear impressions in urine on fabric

“…In order to do so the force applied to create the sample must be controlled and the evaluation carried out in a systematic fashion. A similar approach has been accepted for the preparation of footwear impressions in blood on fabric [19][20][21].…”

“…Computer monitor and colour calibration was achieved and fluorescence photography performed as described previously in the literature [20].…”

“…The protein stains AB1, AV17 and AY7 were initially tested for the enhancement of urine on white cotton and white polyester. AY7 enhancement was also attempted on black cotton and black polyester as enhancement of impressions in blood on dark substrates had previously been successful [20,25,31]. No enhancement, either visual or fluorescence, was observed for any fabric, presumably due to the fact that the proteins present in urine were greatly diluted in comparison to the protein levels found in blood.…”

Development of dry-origin latent footwear impression on non-porous and semi-porous surfaces using a 5-methylthioninhydrin and L-alanine complex

“…Therefore, forensic scientists have developed optical, physical, and chemical methods to develop or enhance Analytical Science & Technology such latent impressions. [2][3][4][5][6][7][8][9][10][11] Of such detection methods, the chemical methods became important in criminal investigations because they not only develop but also enhance latent footwear impressions.…”

A Comparison of Enhancement Techniques for Footwear Impressions on Dark and Patterned Fabrics,

“…Techniques such as ninhydrin and 1,8‐diazafluoren‐9‐one (DFO) have been developed for treating impressions on porous substrates; however, such techniques are designed more for substrates such as paper rather than fabric surfaces, and as such, the choice of techniques might be limited. Previous publications for the enhancement of impressions on fabric have generally been limited to casework examples ; however, more recently, research has been devoted for the enhancement of impressions on fabric by means of both physical and chemical techniques . The enhancement of such impressions is difficult, often due to extensive background staining that can occur.…”