Factual error: After the first victim they claim to have found a shell with 'Megan Turner' on it. That's not possible as we see Ron Silver fire at the victim and immediatley run away. If it had been an automatic then the gun would eject the shell, but it's a revolver, which doesn't eject shells.
Continuity: During a barbeque Jamie Lee Curtis is holding a beer. During the scene the brand of beer changes a number of times.
Factual error: A murder is committed in another room of a house with a .44 Magnum (a Smith & Wesson Model 29, actually, like Dirty Harry's), and no one in the house hears it because it's wrapped in a towel?!?!
Continuity: After Megan shoots the thief out of the window, she walks up to look out of it, and we can see from the reflections that the window as repaired itself.