When I first started teaching criminal law (decades ago), I spent weeks on the Fourth Amendment and the “zone of privacy.” The big case was Katz v. United States, decided in 1967. The FBI suspected that Charles Katz was using a payphone in a phone booth (those enclosed spaces we used to rely on before cellphones) to transmit gambling information to folks in other states (a federal offense). So they attached a listening device to the outside of the booth, which picked up his end of the conversation. He was convicted and, on appeal, claimed that the government should have gotten a warrant before eavesdropping on his conversations. The Supreme Court agreed.

“The Fourth Amendment protects people, not places,” Justice Potter Stewart famously wrote for the majority. In a concurring opinion, Justice John Marshall Harlan emphasized that even if the booth was see-through (as they were in those days), Katz had a “reasonable expectation of privacy” as to the content of his conversation.

Imagine that. A “reasonable expectation of privacy.” Dream on.

My son was shocked by the news that the government is monitoring all of our online communications. He thought he had a reasonable expectation of privacy.

I never imagined that for a moment.

What did everyone think when we talked about “data mining”? You need data to mine.

I must have written dozens of columns since 9/11 about the “delicate balance” between privacy and security. Did people really think I was only talking about other people’s privacy? Did you really believe the “delete” key had that much power?

I’m not trying to minimize the significance of the PRISM leak. Quite the contrary. The fact that a 29-year-old contractor whose adherence to security rules proved to be so lax had as much access to as much data as he did (and we don’t know just how much he really had, because answering that would apparently give away too much) is plenty troubling. Where were the standards? Where were the procedural protections? Who was running this store?

Sen. Dianne Feinstein’s reaction was telling. Feinstein is a San Francisco Democrat, as Ronald Reagan once famously called them — meaning she is about as liberal as you get. She is also the chair of the Senate Intelligence Committee. She knew all about PRISM and immediately defended it as a necessary tool in the war against terror. Critics on the left have been pretty merciless in attacking her.

Is she right? Has PRISM saved lives?

If it has, I’m for it.

If it hasn’t, I’m outraged.

The problem is: How do I know?

If I were playing law professor here, I might go back to Katz and do the number that we lawyers do when we can’t answer the hard substantive question. Go back to process and procedure. Say: Government, get a warrant.

Sure enough. But the truth is, all the government has to do to get a warrant to eavesdrop is ask for one. The chances of a judge saying no are about 1 in 4,000. Sure, forcing people to actually write up an application has value in itself, but if you can put the nouns and verbs together and form a coherent sentence, what judge is going to take it upon themselves to say no? Not many, and understandably so.

I like to write columns where I know the answer. I like to believe there are better answers than telling people to “trust” — that we should, as Reagan himself said, not simply trust but “verify.” But how do we verify? At what cost?

All I know is this: I’m tired of people telling me that politics doesn’t matter, that it doesn’t make any difference who has power in our country. It does. In a world in which courts and citizens alike are unable to verify and have little choice but to trust, it matters.