Plot hole: In the scene where Ashley Judd runs away from her attacker and falls into her aquarium he has moved to the bottom of the stairs - there is no way he would have been able to move that full fish tank. It looked to be about a 30 gallon tank - it would weigh about 400 pounds with the stand and even if he slid it with some superhuman strength, glass tanks are notorious for shattering when you move them full. Plus it would've made enough noise to wake the dead - no way she wouldn't have heard it.
Plot hole: Given that police departments, the FBI, and the CIA do intense screening of potential candidates how did Casanova slip between the cracks? He's clever but surely somebody would've noticed something.
Suggested correction: In truth, there have been plenty of real life corrupt cops, and even cops that were secretly serial killers. If they managed to slip through the cracks, then it's not outside of the realm of possibility that Casanova was able to, too. So this is definitely not a mistake.