After the shootout between Doyle's crew and Morgan and Prentiss, when Prentiss first comes around the corner of the building and the camera shows the dead unsub's wrist, the top two leaves of the clover tattoo are clearly visible. After the break when Morgan picks up the unsub's arm, the tattoo is not visible at all.
When Prentiss is riding in an SUV with Morgan (@ 31:00), her seat belt is slack and halfway down her upper arm. If she were riding in a real car, the belt would be tight and up at her shoulder.
When Prentiss and Morgan are talking in the SUV, they pass a Palm tree. Palms don't grow in D.C.
The subway cars shown in the Washington DC Metro system are different from the ones that the Metro system actually uses.