Originally Posted by MrWally
I've been told multiple times that if a cop asks to search your car and you say no then they automatically have probable cause. It's a broken system, but that's how it is.
That seems a bit backwards-- I mean, if consenting allows them to search and saying no means that they can automatically search, there would be effectively no "protection from unreasonable searches", i.e., it'd be unconstitutional. From what I understand, if you refuse a search, they can detain you for up to around 90 minutes under "reasonable suspicion" while waiting for a sniffer dog (which may give them probable cause to search your car without consent), but more than that and they either have to arrest you or let you go.
To be honest, I don't see a particular downside to saying no to a search request (besides being delayed)-- if you're not guilty, then they shouldn't be searching you, and if you are, there's a decent chance they won't bother with getting probable cause and let you go on your way. In addition, if they did search you without legitimate justification or consent, it's possible that anything incriminating collected would be impermissible as evidence.