Remember there are also different levels of “reasonable expectation of privacy” depending on where the person is at the time of the “criminal event” and what they are doing.
The ultimate area of privacy is the home. This comes from the English common law philosophy that a “man’s home is his castle.” It is the right of a man to be free and unencumbered in your own dwelling. The government must show probable cause to enter a person’s castle. (This is barring exigent circumstances. Every right has an exception.)
The next level of scrutiny would be in a car. There is a much lower level of scrutiny required for the government to conduct a search of a person in their vehicle or the vehicle itself. When you are on the public thoroughfare your expectation of privacy lessons.
Ultimately when a person walks down a street in any city they have NO real expectation of privacy. That is why traffic cameras and security cameras are permissible without anyone’s permission.
The question that will come before SCOTUS, if they chose to address it, is how much privacy is reasonable when it comes to cell phones and the internet. Can you reasonably have any expectation of privacy with a device that is hackable, GPS enabled or dependent upon a third-party server to work? That being said, considering most of us store data in third-party “clouds” does that make everything open to warrantless searches?
Just as a note, most top-flight lawyers will not use emails for final communication or anything that could be considered a client confidentiality. They will not put anything of import in electronic writing. They will not use third-party clouds or use devices that use third-party clouds. They have their own servers and do not go through third parties for anything. (Yes they need the internet for communications. But that is also why they are very circumspect when they use their electronic devices.) These lawfirms even have backup private emergency servers where all the data is stored if the “world comes to an end.”
The interesting idea behind the Bill of Rights as Madison phrased it, is its vagueness. The founding fathers deliberately left the Constitution vague so future generations could decide exactly what kind of society they wanted to live under. They also understood that societies change, grow and develop. I don’t think that Hamilton, Jay or Madison ever conceived of modern technology, but they knew that change was good and inevitable. The question becomes what do we do with change and how do we balance technology with our concepts of liberty, freedom and national security in the age of possible biological/atomic terrorism?