Officer Down - S1-E4
Factual error: Danny and Jackie Curatola are with ESU to make an arrest at a garage. They are behind cover with their weapons drawn. Although there is no suspect shooting at them, both Danny and Jackie have their fingers on the trigger, which is against police training unless you are going to engage a subject by shooting your weapon. The ESU officer right next to them does not have his finger on the trigger. (00:38:04)
Answer: It is an NYPD Detective Bureau lapel pin. If you zoom in on a pic of "Danny Reagan," you will see that the pin has the letters DB on it.