You would need to actually be suspected of a crime. If the cops don't find drugs, what crime are you guilty of?
The usual full expression is something like “probable cause to believe that the person to be arrested has committed a particular crime”.
> "Probable cause" can be used to justify a search.
“Probable cause” is a constitutional requirement for search warrants, arrest warrants, warrantless arrests, and warrantless searches; for searches, the probable cause is that the search conducted will uncover evidence of a crime, which is different than the probable cause for arrest.
> You would need to actually be suspected of a crime.
Well, no, there needs to be probable cause to believe you've committed a crime. Actual suspicion is a much lower standard.
> If the cops don't find drugs, what crime are you guilty of?
There are...like thousands of other crimes, and millions of possible configurations of things that are not drugs that could support probable cause to believe you've committed one of them. Spray paint cans consistent with a recent spate of vandalism (graffiti) in the area is one I’ve personally seen used, beyond things that are inherently actual or apparent contraband, and the “actual or apparent contraband” category extends to more than just drugs.
You can sue anyone, anytime, for anything, but even if charges aren't filed or a court dismisses them at the preliminary hearing stage for lack of sufficient evidence, wrongful arrest suits against police are very difficult.
No, mere suspicion is not sufficient for arrest.
> "Probable cause" relates to searching or entering private property.
It also relates to arrest. The Fourth Amendment provision applying the standard explicitly applies to searches and seizures of persons, houses, and effects. Arrest is seizure of one’s person.
A drug dog’s indications provide probable cause for searching your car, but are not enough to arrest you.
Probable cause (of slightly different things; the threshold is the same but the subject is different) is the bar for both search and arrest.
No, you aren't going to jail unless the search “justified” by the drug-dog “hit” reveals something that the police can spin into probable cause of a crime.
Needn’t be drugs, or even actual contraband.