The critical point is that unless police have probable cause at the scene, they can't just arrest someone and hold them while they investigate. Sounds like they already ruled out alcohol, other issues will obviously take longer to look into. Who knows, maybe he voluntary gave them his phone and they could see that he hadn't been texting or talking. In any event, the Constitution doesn't allow police to arrest anyone, famous or not, just because they think he "might" have been distracted. Let's let it all play out before we draw any conclusions.
