You're on the case as a witness, correct? No don't worry about this- they usually don't do that IRL, at least I've heard of so few cases that you're in more danger trying to buy a bag of crack while stepping out of your 2014 Yukon Denali... Besides (warning, tongue in cheek), there are laws against intimidation and retribution against witnesses... and we all know laws stop bad things from happening.
Besides, you're a gun owner, I hope you have a CCW, I think you'll be okay. Good luck, and usually the DA will help you out, go through the questions you'll be asked, and make you as comfortable as possible.