I'm reviewing a case for presentation to the grand jury: Two police officers were shot at while working a private security job at an apartment complex. They were in uniform, in a fully marked, department provided patrol car, with full arrest authority, but they were not being paid by their agency. Issue: can they still be "lawfully discharging an official duty" if they were not actually on duty? I have contemplated alleging that they were "security officers" under subsection (b)(2)(D) of section 22.02 of the Penal Code, but they don't seem to meet the definition under subsection (d). Any thoughts? Anyone confronted this issue before? Any help is appreciated.

Absolutely it counts as assault on a public servant. This is something that comes up often and is litigated frequently, almost always in favor of finding the officer was discharging an official duty.

Check out Polk v. State, 337 S.W.3d 286, 287 (Tex. App. - Eastland, 2010) for a lengthy citation of past cases from around the state to bolster your position.

Jon, awesome! Thank you so much. I really appreciate it.

You're very welcome! It's something that comes up a lot so I'm always glad when we can get a searchable answer preserved in the forum!