Factual error: After John traveled to hell using Duck the cat, he and Angela are going to eat something and John tells about his suicide attempt. In this flashback, you see them using a defibrillator to shock him back to life. When he is shocked, people are touching his body, but they don't get shocked.
Continuity mistake: When the Mexican is reaching down the hole for The Spear of Destiny we can see him turning his head to the side. When it cuts he is looking down the hole. Also when he reach his hand down his arm goes between a broken plank and the edge of the hole. When it cuts his arm has moved over the broken plank. (00:01:15)
Continuity mistake: When the demon climbs out of the possessed and gets stuck in the mirror we see the reflection of the girl in the mirror and she is smiling with her eyes closed. When it cuts to a close-up of her she is smiling with her eyes open. It cuts again and we see in the mirror she is smiling with her eyes shut. (00:07:50)
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)
Other mistake: In the scene where John is in the apartment with the cat and Angela closes the door, John then says her name to get her to reopen the door. He says the wrong name, "Rachel" (the actress' name) instead of "Angela" (the character's name).
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)
Other mistake: When John puts the needle on the first track of Dave Brubeck's "Time Out" album, "Take Five" begins to play. "Take Five" is the third track.
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)
