Factual error: During one of the cabinet meetings, one of the members says Collins' brief is Minister for Intelligence, but he was actually Minister of Finance. He was, however, the IRA's Director Of Intelligence.
Factual error: When young David and his father show up at Ben Rosen's house, there is a Jewish mezuzah (a handwritten tiny scroll of parchment with a passage from the Bible enclosed in a case) affixed to the doorpost. The position of the mezuzah is incorrect. It should be higher up on the door jamb and the top should be angled towards the house, not the other way round. (00:15:00)
Factual error: When Gotti is outside kicking over trash cans while the surveillance photos are being taken, a series of 1990s vans are seen driving down the street, though the scene takes place in the 1970s.