Re: Vehicle Search Pursuant to Traffic Stop
Nope. His subjective intent is irrelevant so long as there is a lawful reason to stop the vehicle and the underlying reasons is not for some unlawful purpose (such as to harass, get a phone number, or some other reason unrelated to law enforcement).
No, it was because he asked for consent and received it.
Question: not understanding how an expired registration leads to a warrantless vehicle search. Was it because he was unable to produce a license and registration?
Yes, the driver can grant consent to search the vehicle he is driving.
Question: can you give consent to search a third-party's vehicle? It was his mothers and not his.
If the search was not valid, sure. So far, it appears to be good.
Question: if the search isn't valid, are the drugs fruit of the poisonous tree?
Now, if this is homework, you can look up the relevant cases to support these positions.
A Nor Cal Police Sergeant
"Make mine a double mocha ...
... and a croissant!"
Walk humbly with your God
-- Courageous, by Casting Crowns