Plot hole, inconsistancy
I questioned this when I read the book, and the movie doesn't seem to explain it. Amy bought the used car, for cash, from a Craigslist ad. Doesn't there have to be a change of title/registration? If I buy a car, I want the title, otherwise, the seller can report the car stolen, I get arrested, the seller gets the car back, and keeps my money. If I'm the seller, I want the title transferred, so that if there's an accident, or the car is used in a crime, I can say "Hey, not my car, I sold it to this guy".
And if Amy was buying a car that was stolen, she's putting a target on her back that can get her into a lot of trouble.
I realize this is a relatively minor point, compared to other issues, but in real crimes, the criminal is sometimes caught due to minor details (I believe the Son of Sam was caught due to unpaid parking tickets).
"My girlfriend sucked 37 d*cks!"
"In a row?"