Deliberate mistake: When Constantine and Angel are walking to her car the power shuts down turning off all the lights in the street. Then it cuts to inside her car where you can see the lights inside the car is on. When it cuts to outside the car the lights are off. (00:37:35)
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 Constantine gives Angela Isabel's name tag, Angela is holding the tag so that half the tag is between her fingers and the rest of the half inside her hand. When it cuts half the tag is still between her fingers but the rest of the half is now outside her fist. (00:44:30)
Continuity mistake: When Father Hennessy stabs himself with the cork opener the items around him change position between the shots. (00:47:55)
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)
Continuity mistake: When Constantine submerges Angela in to the tub he pulls up his right arm from her head. When it cuts to a shot under water he pulls up his arm again. (01:04:00)
Continuity mistake: After Constantine has thrown the holy water at Baltazar you can see Baltazar stretching out both hands to grab Constantine. When it cuts, Baltazar grabs Constantine by his throat with only one hand . (01:09:55)
Continuity mistake: When Constantine gives Baltazar the final punch you can see Baltazar's tie lying on his chest. When it cuts from behind him his tie is over his shoulder. In the next shot it's back on his chest. (01:10:55)
Continuity mistake: When Angela is standing in front of the elevator and Constantine asks her what's wrong his hand is not on her shoulder. When it cuts his hand is on her shoulder right before she gets dragged through the wall. (01:14:45)
Continuity mistake: When Constantine knocks out the bouncer at Midnite's the bouncer's arms change position between shots. (01:15:25)
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)
Continuity mistake: In the pool when Constantine grabs the possessed Angela, he grabs her by her head with both hands. When it cuts he's holding onto her shoulders. (01:26:40)
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 gets thrown into the glass paned door at the end just before he slashes his wrists, every time it cuts to the scene showing the door the broken glass left in the door is always in a different pattern. (01:32:55)
Continuity mistake: In the scene where John commits suicide by slitting his wrist, the soles of his shoes go from brand new and unmarked (quite clearly seen in a couple of close up shots) to scuffed and worn (also seen quite well in a couple of shots). (01:34:25)
Continuity mistake: In the end when Constantine slits his wrists there is a shot where you see the pools of blood from his wrists. The scene changes for a few minutes and there is another shot where the blood is visible and the pools are smaller than before. If anything they should have been bigger. (01:35:20 - 01:40:50)
Continuity mistake: Near the end when Constantine is on the floor with Gabriel on top of him. There is a shot from the side rotated by 90 degrees so they appear to be upright. There are several things on both Gabriel wrists which look like hospital ID tags. One of them on her left side has slipped down her wrist on to her hand. The shot switches to looking over Gabriel's shoulder and the tag is now back on her wrist and the writing has rotated. Switch back to a side shot and it's back to the original position. (01:35:50)
Continuity mistake: When Lucifer lights Constantine's smoke he has his left arm down, then he closes the Zippo and it cuts. Now his left arm is up. (01:37:05)
Continuity mistake: Near the end, after he slits his wrists, Constantine grabs a cigarette from his pack and places it on his left side. Later, when Lucifer is done with Gabriel and walks back to Constantine his pack of cigarettes is suddenly on his right side and far away from the puddle of blood. When Lucifer wants to grab Constantine's hand the pack of cigarettes is still on his right side but closer and almost in the puddle of blood. And finally, when Lucifer is dragging Constantine away the pack of cigarettes is gone. (01:40:50 - 01:42:20)
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.