Continuity mistake: Right as Agent Smecker shouts "There was a firefight," the Duke is shown briefly. Right before this frame, he (The Duke) already had his guns drawn, yet now his hands are down in front of him, coat closed.
Revealing mistake: When the one man drops the toilet from the top of the building onto the Russian guy, as the toilet smashes over his body, you can tell it is obviously a fake breakaway prop, as the pieces of it are all practically paper-thin.
Other mistake: In the scene when the brother is calling the number on the Russian's pager, he writes down the name of the hotel before you hear the Russian say the name over the phone.
Visible crew/equipment: In the scene where he takes the Russian's guns and bag after throwing the toilet and landing on one, while he picks up his brother you can see a shadow of a boom mic holder on the ground.
Continuity mistake: In the scene where Agent Smecker is doing a gunpowder residue test with liquid paraffin, his left hand starts off on the corpse's wrist, then in the next shot, Smecker's hand is by his chin. In the next shot, it is back on his wrist. In the last shot his hand is back by his chin. (00:12:31)
Other mistake: The brothers executed the "Fag Man" by crossing their guns and the bullets coming out of opposing eyes. You can see when they show the flashback of the execution that the guns are held at nowhere near enough of an angle for the bullets to cross and come out the eyes.
Factual error: In the scene, where Paul Smecker is checking the green trash-bin, he finds a bullet from Ivan Checkov's gun. Nevertheless, earlier (in the plot), or later (in subsequence of the scenes), in the scene, where Connor MacManus is falling down with toilet on Russians' backs, Ivan Checkov, while the toilet hits his bald head, is shooting with his gun, but he misses the trash-bin - the angle of shooting is obviously too extreme to hit the bin. (00:23:34)
Other mistake: In the scene where Connor and Murphy are waiting to hear from Rocco, the phone rings with an "electronic" style ringer, yet when Murphy quickly picks up the phone you hear the sound effect of a mechanical bell being jarred. The same bell is heard when he hangs it back up. (00:54:00)
Continuity mistake: Norman Reedus' Irish accent falters often, particularly when his voice is raised.
Other mistake: In the scene at the bar when the Russian gangsters arrive, Ivan speaks with a heavy Russian accent. In the scene directly after the bar fight, after he kicks in the door to the apartment, Ivan yells his first 4 lines with no accent. (00:07:20 - 00:20:40)
Other mistake: When Paul Smecker tells Detective Dolly: "Well, now that Duffy's relinquished his King Bonehead crown, I see we have a new heir to the throne," "throne" is misspelled on the DVD subtitles as "thrown."
Continuity mistake: After the bar fight, one of the brothers pulls off the toilet and throws it from the roof. But if you compare where he throws it from, to where it hits the people, it doesn't make any sense, the angles just don't work out.
Visible crew/equipment: Just before Conner and Murphy fall through the ventilation duct, the rails used to support the camera can be seen along the bottom.
Revealing mistake: During the scene where Connor is writing down the name of the hotel, you can see his Veritas tattoo smearing.
Continuity mistake: In the hotel scene right before Murphy and Connor pull Rocco in, look at Murphy's gun. The suppressor isn't on straight. Both before and after this shot the suppressor is on perfectly straight.
Answer: Sean Patrick Flanery was the one who had veritas tattoed on his index. He's the one playing Connor. The other tattoo is not Libertas but Acquitas.