Character mistake: When Cole and his mother are stuck in traffic due to an pedestrian accident, a cop ignites a flare to place on the road by the car that hit the pedestrian. The police were already on scene, traffic was gridlocked up and down the street, nothing was moving, and he places the flare about 2 feet in front of the car - a move that is unsafe (potential fuel leak) and unnecessary. It would never be done on a city street, and never in heavy traffic. (01:27:25)
Suggested correction: We don't see the cop place the flare on the ground, the camera cuts away as he leans down with it. It could be assumed that he's putting it down but it's possible he's just bending down to pick something up and has to move the flare towards the ground to do that. Without confirmation that the flare was placed where it's suggested there can be no definite mistake.
Character mistake: In the scene where Denzel Washington and company are beginning to analyze the evidence from the first murder, Washington verbally lists some of the elements found at the scene including the "iron bolt". A little later, someone mentions "by the way, the bolt is iron, not steel" and Washington is surprised.
Character mistake: Mary Ann's mother's name is Janet. At the end when Tom is reading the note she wrote, she misspells her own name as Janent.
Character mistake: The Fifth Amendment Double Jeopardy Clause does not apply. Libby could be convicted of 1st Degree murder when she gets out and pursues Nick. It doesn't really matter to the plot, however, because it was what Libby believed to be true and motivated her. Further, she ends up shooting Nick in self-defense. So it's all good.
Character mistake: In the scene where Maggie tells her sister she is pregnant and how far along she is in her pregnancy, her sister says the child will be a Gemini, just like Einstein. Einstein's birthdate is March 14th, making him a Pisces. Lisa also mentions that Shirley Manson from the band Garbage is also a Gemini, when in fact she is a Virgo.