Hank's attorney does not put anyone on the stand--like Charlie-- who could attest that Hank told them right away that he hadn't known Mia's age. The attorney could also have questioned Mia about why she stole Hank's manuscript, which was because of her annoyance that once he knew her age he wanted nothing to do with her. Mia could also attest to how she picked up other older men, and how Hank tried to stop Lew from sleeping with her because she was underage.