This is from memory, but it's been discussed on HN before, so you can also consult the search bar. Schwartz had a contract to do sysadmin work for Intel. In the course of doing that work, he backdoored some of the systems he worked on. After his employment with the firm that had staffed him at Intel concluded, he continued to use those backdoors to access Intel's systems. His claim is that it was necessary to do so, in order to complete work Intel had asked him to do. But from what I recall, he was caught using those backdoors after any relationship he'd had with Intel had been severed.
It's not the crime of the century, but it's not a case of someone doing benevolent security research getting caught. Nobody practicing today would backdoor a client computer, use the backdoor after their engagement had ended, and expect anyone to find that action defensible.
