
Grand juries are weird in our judicial process. They are secret. They are controlled by the prosecutor. A defendant has the right to refuse to testify before a grand jury but if he wants to, his lawyer can't be present. Doesn't sound very fair, does it? (I know a little bit about them since I ran one for eight years here in Wise County.)
But it's interesting that the Rockwall DA chose to testify. I suspect, and I'd be guilty of this, that he had seen how some grand juries will cut a guy a break if extenuating circumstances are present even if he were technically guilty. They aren't supposed to, but they do. So I bet, being a bit full of himself, that he thought he could go tell his "story" and they'd let him go. Didn't happen.