It also wasn’t long ago that they ruled those dogs cannot be used on the front porch of a residence “just because.”
Scalia is a 4th Amendment champion. So I am not surprised that he joined this opinion.
I don’t know the facts of the case but there seems to be some disagreement in the Court as to whether after the valid traffic stop, the police had reasonable suspicion of drugs. Sounds like the dissent said, they had reasonable suspicion (”suspicion couple with additional objective fact”). It’s pretty settled law that after a valid stop, the police can act further if during the normal process of the stop reasonable suspicion or probable cause arises.