The defense's ability to contest the attribution of touch DNA from the defendant to the crime scene is contingent upon the extent of the DNA profile matching. If a complete match is established, the defense may face challenges in arguing for the possibility of alternative sources. Nevertheless, it is widely acknowledged that touch DNA can be transferred through diverse means, including physical contact with objects and surfaces, or even indirect touch. The duration of touch DNA persistence is subject to external factors such as temperature and humidity.
In an attempt to discredit the prosecution's claims, the defense may posit alternative explanations for the presence of their client's DNA at the crime scene, such as accidental transfer by an unrelated party. However, such defenses will be subject to close scrutiny by the prosecution, and the defense must present corroborating evidence. Additionally, the defense must ensure that any alternative explanations do not contradict the defendant's alibi or the crime's chronology.