I'm going to support an asshole accused on harassment over my friend who accused him
I'm very concerned. Why are you going to support someone that your friend have accused of harassment?
My friend is much less convincing in court.
You should support the person who was harassed, not the abuser. Supporting someone because they are more convincing will make you seem like a horrible friend and you may need to talk to someone about that right after you apologize to your friend.
I want to see what happens
I feel like you're acting in bad faith rather than acting genuinely about the situation. Being in court is a serious matter and you should tell the truth, and if you really think that the accused is innocent you won't call him an "asshole", so I think it's just better that you support your friend and make sure that they would get a fair trial.