How did they find out that Anne Boylen was innocent?

They never found Anne Boleyn innocent. Based on the facts that we have, the perseption of her character, the record of her actions historians have determined that she never commited adulty, incest, or plotting the death of the king as a lot of people back then determined. There is no evidence that Anne ever had sex with anyone but her husband before or during there marriage.

The only confession was from Mark Smeaton who'd been tortured. In some of the evidence saying when and where she'd had sex with five men-including her brother-are flawed. Saying she did this at one palace when she was really at another palace.

Henry wanted Anne Boleyn gone so people found reasons to make her gone.

In any case their marriage was declared invalid before her execution so how could she have comitted adultry when in Henry and the law's eyes they were never married.

To learn more about Anne Boleyn go to TudorHistory.org.