Plot hole: Ruth enters Darlene's home at night, crossing over the crime scene tape. She proceeds to the barn where she finds all of Darlene's heroin packed up neatly. This is factually impossible. Once the police had secured the crime scene in the house, they would have searched the entire property and would have discovered and seized the heroin at that time. (00:54:38 - 00:56:09)
Let the Great World Spin - S4-E2
Visible crew/equipment: Marty visits the FBI agent at her home. The camera starts far away from them in another room, and pushes in through the door frame. On the left side of the frame, the camera's shadow becomes very obvious as the shot moves.
Factual error: Ruth applies to have her criminal record expunged. She meets with the judge privately to discuss the matter. This is an ex parte meeting and would not be allowed. The state's attorney needs to be present for this meeting. The judge also says she will check up on Ruth to make sure she is living right, again without any input from the state. It should be the state's attorney checking up on Ruth, not the judge.
Factual error: The judge rules in favor of Wendy's father despite not hearing any testimony from his primary witness, who fails to appear. The judge states on the record that he is making this ruling because of the Byrdes' "reputation" rather than any testimony. This is absolutely ludicrous. A judge is not allowed to make a ruling on a child custody case based entirely on his opinion of the litigants, which he doesn't even elaborate upon, rather than any evidence or testimony before him.