This answers some questions proposed in introduction part. The consenting party, has the right to give or refuse the consent, and it must be voluntary, consequences and items asked to consent must be explained to the consenting party.
Back to the second condition, what does it mean by having the authority to give the consent? My friend’s USB key is on my computer, do I have the authority? R. v. Duarte (1987) states that “an authorized occupant of a residence may give consent to a search.” Applying this to digital devices, if my friend authorize me to use this USB key, then I have the authority to give the consent to search. However, if he just left it accidentally, I don't have the authority, this is indicated by R. v. Mercer (1992): “A landlord
Back to the second condition, what does it mean by having the authority to give the consent? My friend’s USB key is on my computer, do I have the authority? R. v. Duarte (1987) states that “an authorized occupant of a residence may give consent to a search.” Applying this to digital devices, if my friend authorize me to use this USB key, then I have the authority to give the consent to search. However, if he just left it accidentally, I don't have the authority, this is indicated by R. v. Mercer (1992): “A landlord