They should have brought in Theodoric of York, Medieval Judge.
"If she floats, then it means the water has rejected her and she is a witch. If she is not a witch, the water will accept her and she will sink to the bottom."
"She is not a witch. Ok, next case."
Ha, ha--that's exactly what I was thinking of:
http://snltranscripts.jt.org/77/77rtheodoric.phtml
Joan: Hello, Theodoric, Barber of York.
Theodoric of York: Hello, Joan, Wife of Simkin the Miller. Well, how's my little patient doing?
Joan: Not so well, I fear. We followed all your instructions - I mixed powder of staghorn, gum of arabic with sheep's urine, and applied it in a poultice to her face.
Theodoric of York: And did you bury her up to her neck in the marsh and leave her overnight?
Joan: Oh, yes. But she still feels as listless as ever, if not more.
Theodoric of York: Well, let's give her another bloodletting. Brungilda.
Brungilda: Yes, Theodoric.
Theodoric of York: Take two pints.
Brungilda: Yes, Theodoric.
Joan: Will she be alright?
Theodoric of York: Well, I'll do everything humanly possible. Unfortunately, we barbers aren't gods. You know, medicine is not an exact science, but we are learning all the time. Why, just fifty years ago, they thought a disease like your daughter's was caused by demonic possession or witchcraft. But nowadays we know that Isabelle is suffering from an imbalance of bodily humors, perhaps caused by a toad or a small dwarf living in her stomach.
Joan: Well, I'm glad she's in such good hands.