Factual error: Whistler uses a Heckler and Koch MP5SD3 to mow down several familiars at the vampire library archives, but the muzzle flash is impossibly large and bright for a suppressed weapon.
Factual error: During the subway tunnel fight the subway train takes over 60 seconds to pass by Blade and Quinn. If the train is traveling at 30 miles per hour then the train would have to be a half mile long, or 66 train cars at 40ft per car. A standard subway train is only 8 or 10 cars long.
Answer: I don't think it's so much a memory as it is Blade just equating Karen with his mother in that moment. The only way to convey his thought process to the audience, though, is to show his mother onscreen.
Phaneron ★