Wrongfully acused of a lewd act?

I know someone who was accused of a lewd act. The other person made up this story about how he exsposed himself. There are no witnesses. He has no previous offense of this. The person did this because he saw her physically abusing her son, so I am guessing she made up this story in case he went to the police with what he saw. He is very upset over this whole thing. Is there a chance he will be found guilty?