Danny Reagan catches a ride with his brother and his sergeant in a patrol car. When they find the open subway hatch he gets out off the back seat on his own. Patrol car back seat doors don't open from the inside for obvious reasons.
When three-star chief Jeffords talks to Frank and again later with Frank and the reporter, his collar and shoulder rank shows 3 stars (bureau chief) but his shield shows 4 stars (Chief of Department)
When Erin and Jamie are talking about marriage, Jamie refers to Erin's ex-husband as John. But his name is actually Jack.
Chief Jeffries has three stars and a large brass button on hos jacket epaulets, not four stars.