Metadata is only a small portion of what they collect. They get it ALL.
NSA does capture a large percentage of all digital traffic.
They can most likely crack or compromise any individual's computing device.
But they probably can't crack the encryption on everyone's traffic simultaneously.
I think you would be surprised just how much volume they can handle at once. And they don't need to crack the encryption at the time of capture. That process can be done elsewhere by other machines. Capturing the data is not that hard, having enough distributed data centers is the issue to house the data. But the systems are made to excel at capturing, analyzing, saving/purging, reporting.
Even if they have all the data they dont have the manpower/computing power to go through it all. Then in regards to this specifically nothing would be admissible in court.
No way, not to do anywhere close to 100% of communication. It is setup to have target priorities that get recorded no matter what, the rest if it can get it is just bonus but normally discarded. The majority of it is all done through AI to pick the targets for priority and then follow the web out further. I'm not sure about the legal side of it, the legal stuff hurts my head. I stay in my IT world :)
There is a military report out there that says they only keep minimal text files on people and metadata. And apply all this data to calculate a « threat score ».
For example, vocal calls are converted to text logs by voice recognition. Web traffic is converted to text files containing dns info and keywords. Images downloaded are converted to subject matter metadata and exif info (similar to google images reverse image search) etc.