I automated my job over a year ago and haven't told anyone

I worked as an overnight computer operator years ago, and could easily have replaced myself with a batch script, except for a couple manual tasks that I could have done either at the beginning or end of my shift. I didn't do that, because I enjoyed going to work and being able to work on my hobbies while being paid. The company didn't do it largely out of ineptitude. They'd say they wanted a warm body there in case something went wrong, but one of us was always on-call anyway, even with another of us actually there; no reason the system couldn't just alert the on-call person.

One of our overnight operators worked a second job during his shift. He'd fire up a batch of jobs, go work elsewhere, come back on his lunch break and fire up another batch of jobs, go finish his shift elsewhere, then come back and fire off the last batch of jobs and be there when people started coming for work in the morning. He got caught because he was the only one of us who was always a little behind in his work; so they watched the cameras. When confronted, he admitted it. If he'd have automated the stuff, he'd have gotten away with it for a lot longer.

He can't hire himself to do his own job. Which is what he would effectively be doing by claiming he wrote it "off hours". The very act of writing that script put him "on hours". Now, was it unpaid work? That's a different story. Although since he's also technically not doing work during work hours, one could call it a wash.

If he bought the script, then the company likely needs to reimburse him the cost of that, because its materials for the job. But he wouldn't want to make that request, because then the jig is up.

But then again, we aren't playing "what ifs". There are concrete elements to his story. He did write the script. It is explicitly for this company. It won't work for any other company without large modifications. The non-portability and exclusivity of this script means it was written for the express purpose of doing this thing for this company.

And let's be completely fair here, he cobbled this thing together from StackOverflow snippets. If he's ever found out and fired, even if he takes his script, they're probably looking at a day or two to replicate this work.

The real question for him is would it be worth it? The firm would be minimally affected and could, in turn, make things incredibly difficult for him. This is a law firm. This is what they do. The cost of suing him is negligible, because they already do so much of the work normally. We're really talking about the additional court and filing fees. Whereas, he'd have to retain a lawyer himself. Who would then bill him for all the work they'd do.

Consider, they were paying him $90k to copy files. They have that kind of money to throw at the problem. Do you really want to become a problem?