AbstractFingermarks have been used for centuries as a means of determining an individual’s identity and fabrics have long been considered a difficult substrate from which to visualise and collect fingermarks. This study mainly concentrated on vacuum metal deposition (VMD) and cyanoacrylate fuming (CAF), to ascertain whether these methods could visualise planted marks and consequently be used in the examination of clothing from assault cases. Nine different fabrics: cotton, polycotton, polyester, nylon, nylon-Lycra, satin, silk, rayon and linen along with fifteen donors ranging in age, sex and ability to leave fingermarks were used during this work. The donors were previously tested on paper to determine their propensity to leave fingermarks, which gave an indication as to their donor ability level – poor, medium or good. The samples were collected and processed with the appropriate technique after a
determined time interval, generally, 1, 2, 3, 4, 5, 6, 7, 14, 21 and 28 days, however this was altered for some of the trials. From the results, it was found that both VMD and CAF did visualise marks and ridge detail from latent fingermarks. VMD was found to be the most suitable technique for development of fingermarks on fabric, with gold + zinc VMD best
for light coloured fabrics and silver VMD for dark. CAF also visualised several identifiable marks, even with the problems of background fluorescence from the basic yellow 40 (BY40) dye used to visualise the cyanoacrylate (CA) polymer. Generally, it appears that the smoother fabrics with a tighter weave, such as nylon and silk allowed the visualisation of more detail than rougher and/or looser weave fabrics such as cotton and linen. The latter tended only to show empty marks or marks, which gave indications of where the fabric had been touched.
However, fabrics that did show marks, even if not suitable for identification, could still give information as to the sequence of events that may have occurred during an assault as well as identifying an area to tape for DNA. It was determined that it was possible to collect DNA from VMD visualised marks which led to partial and full profiles of those who touched and grabbed the test swatches or items of clothing tested. Though both VMD and CAF were affected by the addition of water to the surface of the fabrics being processed, marks and ridge detail were still detected, though CAF was less effective than VMD. With sequential treatment, it appears that the optimum sequence is VMD followed by CAF, due to enhancement of
contrast between the metal deposits and BY40 yellow stained background. CAF then VMD only led to extra detail being observed on nylon-Lycra. There was limited success with 1,8-diaza-9-fluorenone (DFO), small particle reagent (SPR), ninhydrin, fluorescent powders or the sputter coater for alternative VMD metals. The production of nanoparticles was unsuccessful; so no fingermark visualisation was attempted. Finally, the issue of ridge detail being obscured by the fabric weave may have been resolved by the use of IR photography or FFT processing. In conclusion, both VMD and CAF are viable processes for the development of fingermark and palm detail on fabric, clothing and textiles. It must be considered however that the donor and fabric being processed greatly affected the level of detail visualised. However, even if ridge detail is not visualised, any marks that are present could indicate a sequence of events or act as an area to target for DNA profiling.
|Date of Award||Aug 2013|
|Supervisor||David H. Bremner (Supervisor)|
Enhanced techniques for fingermark recovery from fabrics
Fraser, J. (Author). Aug 2013
Student thesis: Doctoral Thesis