How often do the people breaking into computers use broken-into computers belonging to a computer security expert who knows how to protect their systems from such break-ins?

I know it's counterintuitive, but all the time. Until only a few years ago, it was almost as if every security expert was being publicly owned constantly. Hackers hack each other.

The dirty secret that explains why they would hack those who can protect their systems: nobody knows how to protect their systems. The best firewall is not pissing off hackers.

In the 20+ year history of computer crime prosecution, outside of this disputed case, what is the next most likely case where a hacker effectively framed another hacker who was then successfully prosecuted for the offense?

Shimomura and Mitnick.... ... ......

Shimomura was successfully prosecuted?

He's being facetious.

I would hope so.

Other way around. I have heard people seriously claim that Shimomura framed Mitnick, though I won't speak to how likely that is.

A pretty hard claim for him to make himself at this point:

https://www.mitnicksecurity.com/about/kevin-mitnick-worlds-m...

You only asked for next most likely, not likely. :)

Anakata was too smart to go after users' computers. He was more of a Kerberos server fellow. Good guy.