When the necktie is tied over Lassiter's eyes, it is above his ears. But in one shot from the side it is below his left ear.
Within at least two scenes, Juliet's nail polish disappears, suggesting that those scenes were reshot well after they were initially filmed.
When Shawn and Gus leave the police station in Gus' car (and they notice that Lassiter is no longer in the car where he was waiting for them), both front seats are missing the headrests. When they arrive at the Psych office in the next scene, both front seats have the headrests attached.
Sergeant Spencer would not be dressing for duty in the 80s with a regular necktie. It would be a clip-on for his safety.
Correction: the regular tie was only to cover Shawn's eyes, as Henry did not take it with him upstairs when he went to finish dressing.
After the shooting, Lassiter, who is well-trained in firearm handling, would have his finger off of the trigger of his pistol. Even if he _had_ shot the prisoner, he would move his finger off of the trigger afterwards.
When Shawn holds the check up and asks the chief to sign it, he holds it upside down and there is clearly a signature on it already.
The coroner does not put Kenny Loggins' body in a body bag before wheeling him to the coroner's van.