While the bite marks on victims are said to be unmistakeably human, the killer actually grows a non-human set of teeth before biting one of her victims.
In the interrogation room, Olivia lays out photos of 3 victims in front of Nicholas Boone. The third shows a body they have not yet found. The victim in the striped blue shirt is not found until later at the waterfront after talking to Mako.
When Dunham is first questioning Nicholas Boone about the two deaths, she shows him two pictures of the two bodies. First of the second victim, and another picture, which isn't identified. Later in the episode, Olivia and Peter have found where the second victim's car was abandoned by the killer. There they find another victim, and both the scene and the victim match the body in the second photograph from earlier in the episode, despite the fact that they just discovered the body.
When Peter and Olivia are in the club scanning the patrons, the ear piece changes from Peter's left ear to right ear and back (possible image reversal).
When Valerie is placed on the gurney, her head changes angle from one shot to the next without her having been moved.
Humans have about 120-150ml of spinal fluid and they produce nearly 500ml/day. Nicholas would have been able to regenerate his spinal fluid many times over while feeding his wife.
The scene when we first see Valerie Boone in the club is repeated later when agent Dunham and Peter go there after they discovered the entry stamps on the hands of the victims.
The opening shot shows that the victim lives above Clancy's Bar on 2nd Avenue in Manhattan, yet the story is supposed to take place in Boston.