First of all, no EMT worth a damn would ever collar someone without also boarding them. Secondly, making the determination in the field about what is best for the patient is not always an easy or readily apparent choice. That is why we have protocols that provide a measure of 'if x then y' to treatment. In the case of a motor vehicle accident, the mechanism of injury dictates what our protocols are. I'll give you an example - our service responded to a man with 'tingling in his extremities'. On arrival he was going downhill fast and by the time he got to the ED he was fully unresponsive and in a bad way. The day BEFORE he was the driver in a car accident where it was hit side on by another car on the passenger side. The passenger's head hit him in the neck. He signed off and refused transport at the scene as he had 'no injuries'. Clearly he did. Last I heard he was in ICU. I have no idea of the outcome. The point is that you don't have X-Ray vision or the clear ability to determine the extent of a patient's injuries in every case. While it may be overkill to board and collar every patient with a certain Mechanism of Injury, it prevents overzealous providers from making judgements without all of the facts. It's not just a fear of litigation that drives this - who among us wants to exacerbate our patients condition if they should have a spinal injury ? Better to be safe than sorry for everyone concerned. Oh, and one last thing. Any patient can refuse ANY treatment. Collar, board, IV, blood pressure cuff. They have the right to say 'no'. It is our duty to inform them of the relevant risks and benefits of treatment.