What finally convinces John Proctor to admit his afair with Abigail in The Crucible by Arthur Miller?

In Arthur Miller's play The Crucible, John Proctor does not make a public admission of having had an affair with Abigail Williams and remains steadfast in his denial even before his tragic execution. However, Abigail herself does publicly disclose his name by presenting the court with physical evidence such as her secret stash of clothes from their liaison hidden under her own mattress, implicating Proctor in witchcraft allegations for a second time and cementing his fate in death.