One of the significant (and ironic) events in Act 3 of The Crucible is when Giles Corey submits actual evidence that Mr. Putnam might be scheming to acquire land lost by those accused of witchcraft.
My proof is there! (Pointing to the paper.) If Jacobs hangs for a witch he forfeit up his property-that's law! And there is none but Putnam with the coin to buy so great a piece. This man is killing his neighbors for their land!
This is ironic because Giles offers actual proof and is dismissed. Meanwhile, any accusations of witchcraft have no evidence but Danforth entertains them all as if they did have proof.
In Act 3, Scene 2, Hale asks that Proctor (and those accused) be allowed to acquire lawyers to argue the case. Once again, blinded by his arrogance and belief of the infallibility of the court, Danforth says that lawyers are unnecessary because witchcraft is "an invisible crime." In completely flawed logic, Danforth argues that only the victims can accuse or not accuse witches.
Now we cannot hope the witch will accuse herself; granted? Therefore, we must rely upon her victims-and they do testify. As for the witches, none will deny that we are most eager for all their confessions.
By this logic, those accused as witches cannot defend themselves. Only the accused can retract their accusations (which they won't because that will put them in jail).
In Act 3, Scene 3, Proctor admits to his affair with Abby to fully embrace the truth and to show how Abby is as sinful as anyone. This would cast doubt on Abby's accusations. This backfires when Elizabeth, in attempts to protect John, claims that no such affair took place. So, instead of making Abby look suspicious, John ends up looking even more untrustworthy.