Researchers aiming to understand how long touch DNA remains detectable on different surfaces under various environmental conditions conducted a study funded by the National Institute of Justice (NIJ).
The research highlights the challenges associated with low and variable quantities of touch DNA collected, making it difficult to accurately assess DNA degradation. However, the findings provide valuable information for forensic scientists and law enforcement personnel. For example, they suggest that DNA is more likely to be recoverable in cool and dry indoor environments compared to hot and humid outdoor conditions. Stainless steel objects may yield better success for obtaining DNA compared to fabric surfaces.
The researchers conducted experiments by depositing control DNA and touch DNA samples on steel bolts and cotton fabric swatches. They examined the DNA residue over time, considering factors like temperature, humidity, and UV light exposure.
The results showed that the amount of touch DNA on both steel and cotton decreased over time. UV light had the most significant effect on DNA degradation for both materials. The amount of touch DNA left behind varied more compared to the control samples. The researchers developed predictive models to estimate the extent of DNA degradation based on temperature and humidity exposure. They found that DNA degraded more in high temperature and low humidity conditions, while it was more stable at low temperatures.
Additionally, the researchers compared the completeness of DNA profiles obtained from touch DNA samples exposed to different conditions with reference samples from cheek cells. They found that DNA samples exposed to UV light were highly degraded and not suitable for forensic analysis. However, under most conditions, touch DNA samples deposited on steel surfaces remained highly stable, except under UV light exposure.
This study provides information about conditions that are more likely to result in DNA preservation. Moreover, attorneys should investigate further if there is an expectation of expert testimony on time of deposition because research is ongoing regarding time of deposition.
Read the article here.
