With This Ring, I Thee Kill! - S1-E7
Revealing mistake: In the hospital, a male nurse stands by as Rhodes talks to the patient, keeping an eye on all the beeping vital-signs monitors. But there's nothing attached to the man in the bed - no wires, no leads, not even an IV.
With This Ring, I Thee Kill! - S1-E7
Factual error: When the girl's injured father dies after speaking to Rhodes, the heart monitor flatlines. The male nurse calmly takes the man's pulse, shakes his head and then just leaves the room - without calling a code blue or making any effort to revive the patient. In 1872, maybe. In 1972, no way.