The man comes to the front door looking for the doctor and is sent away. It is pouring down rain, yet when Stacy looks out the window it is clearly a very sunny day casting shadows. This reveals the downpour was staged for the scene at the door.
The Porsche 928 goes off the roof of the parking garage and rolls freely on its wheels after it crashes. The car clearly had no engine or transmission in it since it was in gear when it went over the edge.
Stacy checks the pulse on the wrist of the dead body and says he was still breathing. She later says he had a pulse. She would not be able to tell if he was breathing by touching his wrist.