New Research Method Leads to Better Touch DNA Recovery and Development of Genetic Profiles
by Douglas Ankney
Touch DNA—“the invisible biological traces deposited through a person’s skin’s contact with an object or other person”—can be found at crime scenes, but detection presents a challenge for officers attempting to recover it. However, researchers M. Recipon and P. Kanemann reported in forensicmag.com that a newly developed method resulted in increased detection of touch DNA and development of DNA profiles.
The materials at crime scenes upon which touch DNA is most frequently deposited—referred to by the researchers as “substrates”—were separated into the three groups based upon their physiochemical properties, as follows:
Group 1 (Roughest substrates)—PVC floor covering and raw wood;
Group 2 (Hydrophilic Substrates)—glass and two types of ceramic floor tiles; and
Group 3 (Hydrophobic Substrates)—sticky adhesive tape, non-sticky adhesive tape, varnished wood, polystyrene, and metal.
Once categorized, the “substrates were tested by developing in vitro models of biological traces, which were similar to the reality in the field, by means of calibrated deposition of cells characteristic of skin keratinocyte cells and fingermarks.”
The researchers successfully detected touch DNA on most types of substrates and demonstrated that the physiochemical characteristics of the substrates adversely impacted the collection of genetic traces. For example, detection on raw wood was difficult because the cells apparently penetrated into the fibers and were no longer on the surface. To compensate, the researchers “developed a universal detection strategy based on cellular-derived markers, where the type of substrate has no impact on this strategy. This detection strategy can be applied to a wide range of substrates, enabling DNA to be localized, better sampled, and optimized for genetic analysis.”
The researchers concluded: “Whatever the substrate, touch DNA could be located and detected thanks to a detection strategy based on cellular and molecular targets, without any impact from the nature of the substrates. This is a new strategy in the forensic world for the in vitro and situ detection of touch DNA.”
Source: forensicmag.com
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