When a Person Commits a Crime, Is There Probable Cause to Search the Person's Phone for Evidence?

The question in the title of this post is one that I've been asked lots of times in different factual contexts. The basic question is, given that most people have cell phones, and that people tend to use their phones to document and to communicate about just about everything that they do, is it reasonable to believe that a person who has committed a crime has evidence of that crime on his or her phone? I don't see that as categorically reasonable. For example, I doubt that most shoplifters document their shoplifting on their phones, so absent some indication to the contrary, evidence that a person acting alone shoplifted an item doesn't strike me as providing probable cause to search the person's phone. But in many circumstances, there will be probable cause to search a suspect's phone, whether with a warrant or pursuant to an exception to the warrant requirement. That's particularly likely where a crime is committed by a group (because the coconspirators may have communicated with one another via text message), or involves a transaction (because the participants may have arranged the transaction using their phones). Courts across the country don't see eye to eye on this, with some wanting specific evidence of a nexus between the crime and the phone before finding probable cause, and others being willing to find probable cause based mainly on the type of offense at issue. Two recent cases illustrate the different approaches courts may take. In United States v. Griffith, 867 F.3d [...]