Near the end of the episode, Quincy, Lt. Markesian, and a sheriff's deputy get into a sheriff's vehicle to chase down the suspect. The car's grille is visible, and the car is a Chevrolet, but when they pull up, the grille now has the GMC logo.
During a search of the suspects house Monaghan finds a shoebox full of child pornography, a significant piece of evidence. Quincy asks if he can borrow the box to show the photos to a victim's mother. Monaghan hands over the box without a moment's hesitation, thereby compromising the "chain of custody". The photos would most likely be challenged at trial.