I also believe that small children don't lie. They don't have the capacity to know what lying is and how to lie in order to hurt others. I've been dealing with the same thing with my daughter. She's 4 and there are some friends and family who believe that she's lying about what happened to her. Well the first incident with my nephew, he eventually confessed after constantly telling us that he didnt do anything. He is 13 years old, he knows what lying is. She doesn't. So it's hard for me to believe that she is lying as well as it's hard for the cops to believe that she's lying. That's why the 31 year old perp that did what he did to her is now in jail. They didn't arrest him based on what my husband saw, they arrested him based on what my daughter told them. So my advice is to look more into what your son told you and don't just let it go.