Well, if she'd been killed before she got in the car, the murderer would have hidden her body in the back. In that case, he couldn't have dumped her out without stopping.
8 seconds sound clip from the In a Lonely Place movie soundboard.
You can hear this line at 00:32:56.806 in the DVD version of the movie.
Quote context
[...]
- You want me to help you solve this murder?
- Brub, you sit down there. Sylvia, you sit there on Brub's right.
- You're the killer. You're driving the car. This is the front seat.
- What makes you so sure this murder was committed in a car?
- Now, you're driving up the canyon. Your left hand's on the wheel.
- You get to a lonely place in the road, and you begin to squeeze.
- You're an ex-GI. You know judo. You know how to kill a person without using your hands.
[...]