What can I do if my friend said my son spit at me, wrote a statement but she lied and he’s in jail?

My son was living with me until he got arrested. He was screaming in my face and spit was going on my face. My friend has seen the way my son gets and she asked me if I wanted her to call the police. I said yes and she told the cops he purposely spit on me which he didn't and wrote a statement confirming it. There were 3 cops that I feel interrogated me asking where did the spit go and how did I wipe it off. At this point, I was extremely confused. I kept telling them he didn't actually spit on me. I didn't want my son arrested. I just wanted him removed from the premises for some cool down time. They arrested him and now there is a no contact order between us since my so called friend lied because she knew he would have been arrested for domestic battery. I am in a very difficult situation.