SGT Preston gives his ID number 120 190 10. (1) It is not an ID Number, it is a Service Number. Service Numbers were discontinued in 1969; they were recited as 12 019 010. This particular number dates from WWII; the number 12 indicates that he was recruited out of Delaware, New Jersey, or New York. (2) If SGT Preston wants to disrespect the detectives by acting as if he is a POW, he would give Name, Rank, SSN, and date of birth.
After taking Sky to the precinct, Rollins is frustrated with her and says, "I could care less what happened to you". This is a common error for this phrase. She should have said "I couldn't care less".
Sgt. Preston needed five stitches after being hit on the head with a lamp, but despite numerous view of his bare noggin, no stitch or wound marks are ever seen.
Sgt Preston has a beard. The US Army only permits soldiers that are members of the Commando and Special Forces regiments are to wear beards but only if based outside their home camps.
When Rollins places Shaughnessy in handcuffs, he is still wearing a large backpack, so in order to be placed in a police cruiser to be transported back to the station for processing, he will have to remove his backpack, which will require him to be released from handcuffs. Rollins should have him remove his backpack before she cuffs him.