Continuity mistake: When Constantine and Chas comes to Midnite's bar and the bouncer holds up the card, we see him holding the card between his thumb, index finger and middle finger. When it cuts, he holds it between his thumb and index finger only. (00:28:30)
Continuity mistake: When Constantine tells Angela to leave the room you can see the cat sits on his lap with its back against the camera. When it cuts the cat is now facing forward. (00:40:55)
Continuity mistake: When we see Chas in his car the first time he lifts his right arm to adjust the mirror. When it cuts you can see he is adjusting it with his left hand. (00:06:25)
Revealing mistake: When Chas is being thrown up and down between the ceiling and the floor, if you look closely as Chas is falling from the ceiling to the floor and goes up again, when he goes up it's just a rewind of him falling down. (01:28:35)
Continuity mistake: When Chas is being thrown up and down between the floor and the ceiling he lands and breaks some bricks on the floor. The damage on the bricks change between the shots. (01:29:40)
Continuity mistake: When Constantine places the medallion on the possessed girl's head she starts screaming and waving her hands. When it cuts to a close-up of her we can see her hand is still. In the next shot she waves her hands again. (00:05:30)
Continuity mistake: When Midnite is about to make a prayer for Constantine he holds his hands up. He only points with two fingers with his right hand. But when it cuts all his fingers are stretched out. (01:20:55)
Revealing mistake: What are the odds for twins to have birth marks on the exact same places? When Isabel commits suicide and lands in to the pool you can see she has the exact same birth marks as Angela to the right above her lips and on her left neck. (00:13:30)
Continuity mistake: When Constantine and Chas gets in to the car and Chas is angry about Constantine dropping a mirror on his car, Chas has his hands down. When it cuts his left hand rests on the steering wheel. (00:10:20)
Continuity mistake: In the beginning when the woman takes the pot out of the oven and is about to pour the hot water into the cup, she places her left hand on the table beside the cup. When it cuts to a close-up her hand is gone. (00:02:45)
Continuity mistake: During the exorcism scene Constantine says "I need a mirror, now. At least 3 feet high.", while holding his left arm down. When it cuts to him shouting "Move." his left arm is up. (00:06:10)
Continuity mistake: When they are luring the demon into the mirror they have tied a chord to it. When the mirror come flying out the window we can still see the chord tied to it. But when it cuts to the mirror falling down hitting the car the chord is gone. And don't tell me the chord just went off, because it was tied quite well. (00:08:15)
Continuity mistake: In the beginning before Constantine gets out of the taxi, he drops a cigarette out of the window. The size of the cigarette differs between the shots. (00:03:25)
Deliberate mistake: When Constantine comes out of the library after speaking with Gabriel, he stands beside Angela and none of them cast any noticeable shadows on the door and walls behind them. When it cuts to a shot above them, shadows are more being cast behind them. This is probably because of different light settings on the set. (00:23:35)
Continuity mistake: In the beginning when the woman is about to pour hot water in to her cup we can see a spoon on the tray. When it cuts the spoon has changed position, and also a piece of paper has appeared on the tray. (00:02:45)
Continuity mistake: When Constantine is looking at the X-rays of his lungs he says "And now I'm gonna be done in by this." and lowers his hand. When it cuts he does the same. (00:14:10)
Continuity mistake: When the Mexican is about to get up he holds onto the Spear of Destiny with both hands. When it cuts it's in his right hand only. (00:01:45)
Continuity mistake: When the Mexican steps his foot through the planks making the hole in the ground, we can see from inside the hole that he is standing directly above it. When it cuts we get a close-up view of the hole outside but the Mexican isn't above it, he is moving closer to it. (00:01:10)
Continuity mistake: When Constantine is having his chat with Gabriel, after he asks what 'He' wants from him, and Gabriel says "Only the usual. Self-sacrifice. Belief.", it cuts and we see Gabriel resting her hands on her lap. When it cuts her left hand is on her knee. (00:21:55)
Deliberate mistake: When Constantine and Angela are driving while talking to Beeman, as Beeman says "But that doesn't mean that we don't have faith in you", the lights in the car suddenly go off. Revealed by the DVD commentary, it is the cinematographer's lights going off by mistake. (00:57:50)
Answer: Sin for a good reason is still sin, and as Gabriel says earlier, you can't buy your way into Heaven. Real Catholic dogma, however, doesn't hold the mentally ill as condemned for committing suicide.
Greg Dwyer
Except Isabel wasn't mentally ill. She saw angels and demons just like Constantine did. It was her parents who believed she was mentally ill.
While suicide is a mortal sin, it's shown later (as in major plot point) that sacrificing yourself to save the world is a redeeming act.
Yes, but Constantine also said "My parents were normal. They did what most parents would do. They made it worse. You think you're crazy long enough, you find a way out" which could relate to Isabel losing her sanity in a way as well because of her family and how they saw her. The whole Isabel's sacrifice is added by the novelization but the movie is ambiguous about the suicide.
mp1920
Except Isabel wasn't mentally ill. She saw half breeds just like John did.
Sacrificing yourself for others isn't a sin.