The entire film happens over three weeks' time, but when it's mentioned that William is in a coma, which occurs at the beginning of the movie, Roman states that he has been in a coma for several weeks already.
When Roman leaves Harrison's office after speaking with the niece and George, he angrily closes the door to his own office. When George goes to talk with Roman after the niece has left, Roman's office door is open.
In the beginning of the film, George Pierce (Colin Farrell) is driving his BMW with the new California Legacy (black background, gold lettering) license plates; at film's end, he's driving the same BMW but with the standard California license plates (white background, blue lettering).
When Roman and Maya find a dead homeless man on the sidewalk, a police car approaches them and the lights on the front of the car turn on. The film is set in Los Angeles, California and the police car's lights do not display a steady red light. In the California Vehicle Code, all police and emergency vehicles in California are required to have at least one steady red light facing forward when the flashing lights are on.
When Roman is driving the U-Haul, the radio on the dash that is shown is an AC Delco, which is factory equipped in GM vehicles, however, the U-Haul is built on a Ford chassis. Ford vehicles do not have AC Delco audio equipment.
George would not say, "Filing a federal brief in District 9," as he was in the District 9 federal courthouse and all cases heard there are federal cases.
At about 0:49:48, as Roman and Maya are assisting the possibly-dead homeless person, Maya receives a call on her cell. When she "answers" the call the screen goes to sleep. During the call, the screen illuminates because of movement and reflects on her face. Neither would happen if she were actually answering, then using the telephone feature on today's smartphones.
A lightning bolt is seen during a thunderstorm, from some distance. The sound of thunder is heard simultaneously. The sound should follow several seconds after seeing the bolt.
In the middle of the movie when Roman J. Israel exits a taxi, the camera is visible on the window of the cab.