When Hallman's third victims pull up to their house in a Cadillac, the brake lights (and taillights) turn off when the car is turned off. Actually, a GM vehicle will turn its reverse lights on when the car is turned off (as well as its headlights and taillights), then turn everything off when the doors are locked. This Cadillac is not shown doing that.
The plane identifier on the engine was reversed. This is not the first time this has been noticed this.
Many of the driving scenes have palm trees in the background. There are no palm trees in the Seattle area.
When the unsub kills the lone foster mother, the unsub shoots her several times as she's on the floor. But when the BAU is at the victim's house investigating, there is no blood at all around or on the victim's body.