The "Jaws of Life" (spreaders) are used to spread parts of a vehicle or object to gain access to the patient(s); they are not intended (nor safe) to be used as a lift. For lifting a vehicle, a combination of wheel chocks (to reduce lateral movement), wood blocks (to support the vehicle after being lifted), and air bags (to do the lifting) is necessary. These items need to be operated by persons trained and experienced in their use.
I have seen cases in which a vehicle was lifted from a living patient's lower half, and the patient then dies almost immediately. If a heavy object/vehicle is on the patient's chest, then there is a probability of sufficient chest trauma to kill the patient within a short time.
What was the patient's actual cause of death?
