Continuity mistake: When Angelina Jolie destroys the mirror, you can see (just freeze the shot for an instant) that the mirror has been broken completely. Yet, in the next shot, she watches her reflection and there's still a lot of mirror unbroken. (01:31:30)
Continuity mistake: When Angelina pulls up in front of Ethan's apartment she hears 4 shots from inside. During the replay, when the viewer sees how things really happened, there are 5 shots. (01:10:25 - 01:31:20)
Continuity mistake: At the end of the film when Agent Scott stabs James Costa in the heart with the scissors, he first falls onto his knees and then backwards as he dies. In the next shot you see James Costa laying flat out on the floor. When he fell backwards his legs should have remained folded under him. (01:42:50 - 01:43:40)
Continuity mistake: Keifer initially grabs Ethan's neck with his right hand and pins him up against the wall with it, but for the rest of the scene he's using his left. (01:08:50)
Continuity mistake: When Angelina goes to the scene of the murder witnessed by Ethan, she is seen sitting on the footpath. At the start she has a pad on her left knee and a pen in her left hand. However as the scene progresses, it disappears and reappears several times. (00:23:35)
Continuity mistake: When Ethan and Angelina struggle with the scissors, he initially grabs her left wrist and pins her right arm to her chest behind it. Then for the majority of the scene, her arms are reversed. When he stabs her, it's back to the original position. (01:42:25)
Continuity mistake: When Ethan is holding Angelina, he holds up the scissors with his right hand to her, but in the next shot his right hand is by his side. (01:36:20)
Continuity mistake: In the car chase, Kiefer Sutherland is pointing a revolver (notice the barrel, sight size and rear hammer-cock) at Ethan Hawke. During the review sequence near the end, Ethan Hawke is shown placing a pistol, not a revolver, into Sutherland's hand.
Continuity mistake: When Angelina crashes the Mustang, her jacket gets caught on something near the console. There is a steering wheel airbag visible in all but the one shot where she reaches over and rips her jacket. (01:12:45)
Continuity mistake: There are 2 shots during the car chase that show the gun being held up above the passenger's shoulder level. In the event replay, we see Ethan seat belt Keifer's arm so it's cradling the gun pointed towards the driver's side. In this shot, the gun appears to be resting against his shoulder with just the barrel sticking out. (01:11:30 - 01:31:20)
Continuity mistake: When Angelina is sitting on the footpath at the scene of the murder witnessed by Ethan, a little girl and her mother walk by. As Angelina spots the girl looking at the open folder with the pictures, she reaches with her right hand to close it. Immediately the shot switches to over her left shoulder and she is closing it with her left hand. When the shot switches back again, she is again closing it with her right hand. (00:23:50)
Continuity mistake: At the very beginning when the bus breaks down, there is a building marked 'Repairs and Rentals' on the left side of the bus. Then Martin looks out of the right side of the bus and sees the same building there. Two buildings exactly alike? I think not. (00:01:45)
Continuity mistake: During the love scene Ethan has his left hand on Angelina's throat, but then it changes and it is his right hand.
Answer: Yes, he must do this to truly feel like the different person he is trying to be. Also, so the police won't suspect anything if his traits don't match his identity.