Is expiation for fasting obligatory for someone who caused the death of a truck driver by operating the truck at the driver's own direction, moving the gear stick, which led to the truck lurching forward and the driver's death?

If the driver ordered you to disengage the gear lever and you disobeyed, then you are responsible for his death, and you must pay the blood money (Diyah) and perform expiation (Kaffarah). However, if he ordered you to move the lever in a way that would cause the car to move when started, then you are not liable for anything, unless his death was due to your moving the car away from him, in which case you are liable for the blood money and expiation.