Can I testify in my parents Divorce Trial?

My Mom is suing my Dad for divorce. Can I testify in favor of my mom against my dad, so she takes his money? He is such an asshole, I cannot begin to explain, and we both believe he is bipolar. He treats us like **** basically. He acts like he's a good dad too which is ridiculous. It has gotten to the point where i told him I was going to kill him, thats how bad he is. My mom has no job and he always threatens us financially because that is his only hold on us. I try to have a relationhip with him but I can't. Sorry this is disorganized but I got into a huge fight with him a few minutes ago and I'm just typing my thoughts. i cannot begin to start about how bad of a dad he has been. Basically he had a bad childhood, and takes it out on us now. He seems to have so many problems, and he never can get work done. He threatens me all the time with financial stuff and just walking out and leaving.