What determines if a person must go to Grand Jury?

About 6 months ago my boyfriend was arrested for statutory rape with 13 year old girl. He's 18 and has no other charges against him. The sex was completely willing, but her parents still had a rape kit done on her. They couldn't prove that it was him because he wore a condom and I'm not sure if they ever found liable evidence that she had even recently had sex. He met with her mother and apologized, and she agreed to drop all the charges and defend him in court. He is out on bond right now and has been for several months; however, his bonding agent is going to call in a few weeks to see if he has to go to court. My mom, who really doesn't like him and could just be making this up, says that he has to go to Grand Jury and is facing 5 years. And if there's any constellation to this, we live in a very small town in Mississippi, and most laws are barely even enforced. I don't have very much knowledge about court and laws so if anyone could help explain this a little better to me and tell me what will more than likely happen based on past experiences or just basic understanding of these situations, PLEASE let me know!!! Any answers at all will be extremel appreciated! :)