What is a key factor that invalidates consent given during an illegal detention?

The key factor that invalidates consent given during an illegal detention is the coercion or illegality of the stop. When individuals are stopped by law enforcement without reasonable suspicion or probable cause, the initial detention is considered illegal. In such cases, any consent given post-detainment may not be deemed voluntary, as the individual may not feel free to refuse or withdraw consent due to the intimidating circumstances created by the illegal stop. The coercive atmosphere inherently affects a person's ability to provide true and informed consent, rendering that consent invalid in legal contexts.

Options related to the presence of witnesses, volume of police presence, or time of day do not address the fundamental issue of the legality of the stop or the genuine nature of the consent, making them less relevant in determining the validity of consent.