open court case, not getting the job?

Natasha
My boyfriend is in this bind where he has child abuse charges filed against him. But he didn't abuse any child. His 16 year old sister and him were fighting eachother one day, she attacked him first and beat the bloody crap out of him. The only thing he did was hold her down to prevent her from further hurting him. I came and pulled them apart and she went and called the police. The police came and took her side. She didn't press charges but the cops did. So now he's in trial against her. So he had applied to a well paying job, passed the drug test except the background. The HR said that there was a charge and case for child abuse, so we cant hire you. He called his lawyer and he said, the employers cant see the rap sheet.. only what was finished. He thinks someone called in and told the employer the situation so he cant get the job. Someone being my mom cause they dont get along, but i dont think its her. How do background checks workand what can they see on there? the case is still open and he wasn't convicted of anything. It's filed under misdemeanor not a felony but it's a criminal case. So I can I tell him or prove that it wasnt my mom?