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P236 – Seeing the Unseen: Visualising DNA-Containing Material on Vehicle Surfaces
Motor vehicles are frequently associated with criminal activity and are routinely sampled for DNA to support investigations by identifying individuals who may have interacted with vehicle surfaces. Currently, no validated tool can successfully visualise DNA not attributed to a body fluid, known as trace DNA. As a result, investigators must utilise their experience and background knowledge of the case to target areas they believe will yield sufficient DNA. DiamondTM Nucleic Acid Dye (DD), a surface-based DNA-binding dye, has been proposed as a potential tool to assist in the localisation of DNA-containing material (DCM) prior to sampling.
This study evaluated the effectiveness of different DD formulations and visualisation tools for detecting DCM deposited on external vehicle surfaces.
To simulate high and low level DNA deposits, saliva (n = 5) and fingermarks (n = 5) were applied to each of the seven distinct vehicle surface types – airbag, boot piece, bumper, headlight, mirror, taillight and wheel guard. DiamondTM Dye formulations at concentrations of 20x and above were assessed using deionised water, hydrofluoroether (HFE), and varying ethanol concentrations. Visualisation was conducted using a Dino-lite® microscope and a Polilight® equipped with a 555 nm interference filter and a 550 nm cut-off filter.
Statistically significant differences in visualisation success were observed across dye formulations, surface types, and visualisation methods for both saliva and fingermark deposits. Optimal detection of DCM was dependent on a surface-specific combination of DD formulation and visualisation tool. Across all surfaces, the Dino-lite® microscope consistently ranked among the top-performing methods.
These findings demonstrate the potential of DD to assist in the visual identification of DNA-containing material on vehicle surfaces, offering investigators guidance on where to target sampling to maximise DNA recovery. However, due to safety limitations associated with higher dye concentrations, the use of DD is recommended only under controlled laboratory conditions. At present, DD is therefore unsuitable for frontline crime scene deployments.
Authors
- Katelyn Hare (University of Technology, Sydney, Australia)
- Georgina E Meakin (University of Technology, Sydney, Australia)
- Alicia Haines (University of Technology, Sydney, Australia)
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