During the opening locker room scene, Officer Taylor states "this is the department issue sidearm; Glock 19." The gun he holds up to the camera, however, is clearly stamped "22" and ".40," indicating that it is not a 9mm Glock 19 but instead a .40S&W Glock 22.
When Van Hauser and Sook come to release Taylor and Zavala to go back on patrol, after he goes under the tape he takes his cigar out of his mouth he spits. This is an official crime scene, that's whats "called leaving your own evidence on the crime scene". Professional police officers don't spit or leave any of their bodily functions on the crime scene. That confuses the case.
During Brian and Janet's wedding, Zavala asks Taylor "Why did you get married in your dress blues?" But Taylor gets married in a suit, not in his dress blues. There is a deleted scene of Taylor getting married in his dress blues.
When they are driving and spot the fire they help with the dispatcher asks for a location which they identify at 1002 6th St. During the scene following at the house that they find the human trafficking ring, they ask for backup which the dispatcher calls for additional vehicles to respond to 1002 6th St. A minute earlier, they had identified this house as "9318 53 Street".
As Taylor and Zavala drive towards the house they set out to search, there is no passenger cage in the vehicle they are driving. However as they exit the vehicle, another shot shows their vehicle to be a marked Police Interceptor with a passenger cage installed.
When the 2 officers are performing the "Welfare Check" on the house, right as they are about to kick in the door the reflection of the window to the left of them shows a blue tent and several crew members in the back behind the scene.
During the locker room scene, Officer Taylor states the standard issue sidearm for the LAPD is a Glock 19. This is incorrect, as the standard issue sidearm is a Glock 17 (9mm) issued to recruits in the police academy which they must carry for their one (1) year probationary period. After successfully completing their probation period, officers can then purchase and carry a firearm of their choice off the department's "Approved for Carry" list, which includes the Glock 19.
When showing the burned up stolen vehicle the officer states they found two types of shell casings, 9mm and 45. However, the brass they find is 7.62x39mm, 9mm, and .45 ACP, correlating to the three calibers of weapons used in the drive by scene.
The goof item below may give away important plot points.
In the very last scene of the movie, after the funeral, the driver's side sun-visor goes up and down several times on its own. In one shot of it down, there is clearly some audio equipment visible and in the next shot it is gone.