Recovery Of Dusty Shoe Prints From Human Skin: A Literature Review

Recovery of dusty shoe impressions from the skin is a fairly unchartered territory of research, and thus, there is a limited number of articles related to this subject. This therefore creates quite a huge gap in this field of knowledge, and makes any comparison between different researches conducted to fall short of being comprehensive. So far, articles written on this topic can be divided into two: impressions on lifeless (cadavers) and living bodies. One common method of lifting has been used in both instances, whereas in one of the instances more methods and further enhancement was carried out.

The articles can also be divided into two on the basis of the prints being latent (invisible) or patent (visible). In this article, two articles that focus on patent impressions made on a cadaver and on a live person will be reviewed side by side, and a critical analysis of the methods chosen and results obtained analysed. Background Adair & Dobersen (2006) conducted experiments with a human cadaver to establish whether dusty shoe impressions could be lifted using an ESDL from human skin ESDLs can be utilized to lift both impressions, both latent and patent, from a diverse range of porous and non-porous surfaces. ESDLs work by passing a charge across a metallic film that has been placed over the dust print. The charge creates an electrostatic adhesive force that pulls the film to the print-bearing surface, and this causes the dust particles to be transferred to the film and to adhere to it. The dust particles are retained on the film even after the charge is turned off because the film retains a charge. ("Forensic Science - Electrostatic Dust Print Lifter", 2018). A rubber roller pad may be used to smooth the film to eliminate any pockets of air.

This process is not destructive to the evidence, but is not recommended for lifting wet impressions, such as those made by blood. On the other hand, Shor et al. (2014) used human volunteers and lifted the dusty prints using ESL, gelatin lifter and adhesive lifter before enhancing the print chemically using BPB. BPB is a pH indicator with a useful range of between 3. 0-4. 6 that can be used for enhancing 2-D dusty shoe impressions after being lifted with low tack adhesive lifters (Bodziak, 2017). The dust particles change colour to blue when sprayed with BPB in the reduced form. Materials and Methodology Human skin Adair & Dobersen (2006) used the skin of an adult male human cadaver whose death was from natural causes, and there was no pre-existing trauma to the areas of the body on which the tests were conducted. The cadaver, previously refrigerated, was kept at room temperature (68oF) for several hours so as to make the skin easier to work with when rolling out and lifting the film.

The warming of the body was however not a factor for the functioning of the ESDL. Conversely, Shor et al. (2014) used a live volunteer. They endeavoured to simulate natural stepping on a live body at a crime scene as opposed to stomping. Process of Application of Dusty Print Whereas Adair & Dobersen (2006) simply went ahead to dust the sole of shoe used to create the impressions by walking around in the garage of the coroner’s office, Shor et al. (2014) first cleaned the shoe soles of the shoe that would be used by stepping it on an adhesive lifter before finally dusting the sole. Adair & Dobersen (2006) conducted tests on the arms, legs and trunk of the cadaver; and impressions were made using both heavy and light pressure from the hand. Impressions were let to sit for one hour before any attempt to lift. On the other hand, Shor et al. (2014) deposited the test prints only on the foot of the volunteer. Standard protocols of photography were conducted before lifting.

Lifting Methods Adair & Dobersen (2006) used a Kinderprint model 3C and a Sirchie modl ESP900 lifting devices for all experiments. They both operate in the same manner with similar results produced, with the only difference being that the former is lager while the latter is a hand-held unit. The metallic lifting sheets were secured onto the body using masking tape, and were aligned with the long axis of the leg. The film was rolled from the apex of the arch of the limbs outwards to minimize formation of air bubbles. Shor et al. (2014) used three lifting methods: ESL using a black aluminium sheet, a black gelatin lifter (BVDA, the Netherlands) which was pressed against the mark for a few seconds and then lifted, and a white adhesive lifter (JAC vinyl adhesive) which was pressed against the mark for a few seconds before being lifted and recovered with a silicon cover. Enhancement Only Shor et al. (2014) conducted an enhancement on the test prints.

The adhesive lifter was further enhanced with BPB after lifting. Number of Lift Attempts Adair & Dobersen (2006) attempted a second lift on the legs. These were successful with very little loss of detail. They however made no attempt at further lifts on the arms and trunk. On the other hand, Shor et al. (2014) tried each process three times. Results In Adair & Dobersen (2006), the lightly pressed impression was difficult to see as compared to the heavily pressed one prior to lifting. However, the quality of the impressions after lifting was good enough to be used in making an identification as it showed individual characteristics as well. It was noted that body hair and debris could impart artifacts on the lifting film, and hence be mistaken for characteristics of the outsole. In Shor et al. (2014) there were more results to be obtained owing to the more expansive experiments carried out. The black gelatin lifter produced the best results in terms of wholeness of the impression, precision of detail and contrast.

With ESL, the curved nature of the leg could not allow full contact with the lifting film, hence the impression was not lifted wholly. BPB on the adhesive lifter reacted with both the background and shoe print, hence part of the dusty print was concealed. In comparison only on the basis of ESL, Adair & Dobersen (2006) obtained better results with their lifts as compared to Shor et al. (2014). Discussion ESL is not the most feasible method for lifting shoe prints from live bodies because although it may not be harmful to one’s health, it is still uncomfortable and dangerous. Additionally, it is not easy to establish full contact with the lifter due to the curved nature of the foot. This may explain why it was simpler to apply this technique with more ease to a cadaver than a live person, and thus may be used to rationalize why Adair & Dobersen (2006) obtained better results with this method. When the adhesive lifter was sprayed with BPB, it immediately turned blue and masked large portions of the print. This prompted the authors (Shor et al. (2014)) to apply the adhesive lifter on a clean area of the volunteer’s skin, and lift then spray with BPB.

The lifter turned blue, and the design of skin cells appeared on it. The human skin has a basic pH, and thus when microscopic skin cells are lifted by the lifter, it turns blue when sprayed with BPB. This is thus not the most suitable method of lifting dusty shoe prints from human skin, unless the shoe print contains a considerably large amount of dust, and the characteristics of the shoe are very big. The black gelatin lifter turned out to be the best of all the three methods used by Shor et al. (2014). Because of the flexibility of the gelatin filter, it was able to lift the prints even from the curved surfaces. Conclusion ESL was the only common technique between these two articles. It worked best on the cadaver as compared to the live volunteer. It is not the best method for live persons, as full contact is not easy to obtain especially due to the curvy nature of the body. The electric charge may also harm the person.

However, care must be taken with the cadaver so as not to confuse any hair and artifacts on the skin that may have been lifted with shoe sole characteristics. Of the additional methods used by Shor et al. (2014), the black glatin lifter was the best because it could lift the print even from curved surfaces due to the flexibility of the gelatin. The prints obtained were also very clear. Adhesive lifter enhanced with BPB is not the best with dusty shoe impressions on skin, because it lifts microscopic skin cells as well, and these react with the BPB to produce a blue colour that will conceal the shoe print. It is not clear whether cleaning the sole of the shoe before the experiment by Shor et al. (2014) had any significant impact on the resultant impressions. It is important to note that because dusty shoe prints are quite fragile and at times there may be challenges associated with lifting them, it is critical to take good quality initial photographs of the impression before any attempts are made to lift them.

In conclusion, there is not enough research done to establish how best dusty foot prints can be recovered from human skin, hence more studies, research and experiments need to be conducted to expand the knowledge in this field. This will be especially helpful in future for cases that may involve crimes with the opportunity of shoe print transfer onto the skin such as stomping on a person, kicking a person or restraining a person using one’s feet.