As Gideon is preparing to enter the building and confront the unsub, he puts on his bulletproof vest and starts toward the building. The camera changes angles and we see him briefly pass by with his vest in his hand. Then a third shot shows him putting on his vest again.
After the killing of the priest in the church, Jason Gideon puts on a rubber glove before touching the knife blade in the head of the victim. As Gideon puts on the glove he clearly rips it accidentally. In the next closeup of Gideon's hand, the glove is without tear.
After the unsub releases his hold on the hostage, the alternating scenes show him gripping the pistol in his right hand, then in his left hand, then back in his right hand again.
When the team enters the vigilante's apartment, they observe boxes of case files, identified by the name of the case. Several boxes are marked "N.Y.C. v. 'Name'." Since it's unlikely the vigilante would be hunting jaywalkers or persons who were accused of other similarly-trivial offenses, the city would not be the prosecutor in any of the cases; the state would be.
While eating with chopsticks, Spencer asks for a fork. While JJ is offering to help, the table is shown, with Morgan on the right and Spencer on the left. There is clearly a fork on the table, between them, yet Spencer doesn't use it.
Spencer talks about the Bernhard Goetz subway shooting in NYC that took place in 1984. Gideon replies "You weren't even born". Matthew Gray Gubler was born in 1980. Spencer mentions that he is 24, which puts his birth around 1981-82.