There really isn't a fourth amendment issue.
I do still disagree with the District Attorney's statement. We can write something on a piece of paper and burn it, or think something in our heads, and keep it private. That this is now possible with digital communications via encryption is not a new right, it is simply a new means to protect that right. Further, Apple didn't invent encryption, and this statement further shows how little the DOJ understands about technology.
Wait, is he actually arguing that the right of privacy didn't exist until a few years ago? There's literally decades of precedent, including digital precedent, for a right to privacy.
What's at stake here is the power of government to compel testimony. They already have the phone, but they lack the power to compel its unlocking.
That's not how rights work.
I'm not saying criminals don't deserve rights. In fact, what's at stake here is that the Fifth Amendment does protect a mass murderer from revealing his passcode, so I'm not sure what you and all these downvoters are going on about. If criminals didn't have rights there wouldn't be an issue here.
If the passcode on the phone were crackable, it would be absolutely 100% legal to search it. And that kind of thing happens routinely. The issue at stake is not searching the phone, but compelling Apple to help with the search.
> "Apple has created a technology which is default disk encryption. It didn't exist before. It exists now. Apple is now claiming a right of privacy about a technology that it just created. That right of privacy didn't exist before Apple created the technology." [1]
Wrong. The first and fourth amendments grant rights to privacy. The exact transcripts of what we say in the privacy of our homes, prior to a warranted wiretap or without witness testimony, are not the subject of law enforcement's investigation. Our entire history of digital communications should not be open for government surveillance. It would be overreach to try to implement, and anyway it is impossible to guarantee without destroying the US tech industry and turning us into a big brother state.
[1] https://youtu.be/g1GgnbN9oNw?t=4h46m22s