so the crux is that the police can not force a citizen to facilitate the CREATION of evidence. Police may only collect it as it sits.
Then the argument is over what constitutes existing evidence. If your breath contains an undue percentage of alcohol, that’s evidence - which exists, the breathalyzer simply acquires & quantifies it. We’d have to objectively define a limit to such acquisition (sticking device in one’s mouth, vs sampling air inches away).