Isn't there a field breathalyzer??? If not, It would not be an obvious sign of guilt. Just a tacit sign. IMO sober people don't refuse it.
Wouldn't he have been arrested and immediately tested downtown? If so, maybe we are still waiting for the whole story.
You can refuse a field breathalyzer. The only test you are 'required' to take is a BAC and that is AFTER you have been arrested.