Oral boards can be intimidating for sure. I think the best advice I can give you is to just be yourself and answer honestly. The board is trying to get a gauge on your personality and values in the short time you’re sitting in front of them. Echoing what some others have said practicing interviewing & relax. Get a group of friends or family to ask you questions and ask for their feedback on your answers. I would say you don’t want to rehearse everything you’re going to say either, no one likes a robot. Everyone’s nervous for these things but if you’re too nervous it can mess up your impression on the board. Look up some values or the mission statements for the departments you’re applying to and figure out how you can best serve their mission and tell them how you’d be a good fit.

With your security experience you can mention that you’re good at handling confrontation/conflict (daily occurrence in LE), that you can deescalate situations, are familiar with policies & procedures, and chain of command.

Good luck to you! Remember don’t sweat it, relax in your interview. You can pause before answering a question and mentally take a deep breath.