When Rita and Dexter are inside the shed, the window blind is partially open. When they go outside to lock the door, the blind is fully closed.
Deb's hair goes from being behind her right ear to in front and back again during the conversation with Quinn at about the 20-minute mark.
The type of cut Dexter sustained on his knuckle would continue bleeding far more profusely than is shown. It would also require stitches.
Arthur claims he's holding up the mirror in such a way that his wife can look at her own reflection. This is inaccurate. The audience can see her face centered in the mirror, which means the actress is looking at the camera's reflection instead.
When discussing the DNA, Dexter and Masuka say that the cremated-bone DNA could come from a female related to Trinity, either his mother, sister, or daughter. This is incorrect. Mitochondrial DNA, which is the DNA that the two samples share, can only be passed down from mother to children, so Trinity's daughter would not have this shared DNA, only his mother, sister, or brother. Also, Mitochondrial DNA does not indicate the sex of the person.
(at around 39 mins) Dexter sits at his desk and looks over a flyer given to him by Trinity. On the flyer, the word "rejuvenating" it spelled wrong. It says "rejuvinating."