Warrentless cellphone searches are reasonable if only it falls within a specific exception to Fourth Amendment's warrant requirement. See Kentucky vs King.
I looked up Kentucky vs King on wiki. TL;DR warrantless searches conducted in police-created exigent circumstances [0] do not violate the Fourth Amendment so long as the police did not create the exigency by violating or threatening to violate the Fourth Amendment.So, does that mean if police knocked on my door suspecting I might delete sensitive data on my phone before they get to it, are they still allowed to do warrantless search of my cell phone?
[0] http://en.wikipedia.org/wiki/Exigent_circumstance_in_United_...
EDIT: DO not start fucking downvoting just for the heck of it. May be I didn't understand it well, does that mean I can't ask a question here?