What is the burden of proving negligence against a defendant in a motor vehicle accident case?

The general rule, of course, is, that he who alleges negligence must prove it, and negligence on the part of the defendant is essential in cases of this sort to the success of the plaintiff’s action. There are cases in which this obligation upon the plaintiff is dispensed with and the onus of showing that he was not negligent is cast upon the defendant. For instance, a man walking down a street who is struck by a barrel or a flower-pot falling upon him from a building cannot be expected to show that the object fell through the negligence of the occupier of the building or his servants (Byrne v. Boodle, 2 H. & C. 722, 33 L.J. Ex. 13). The fall may have occurred through the breaking of a support, or the negligent or malicious act of some person, but the circumstances are entirely beyond the knowledge of the plaintiff, and the evidence which explains them, if it exists at all, is in the possession of the defendant. The law, therefore, does not require the plaintiff to do more than he can in reason be expected to do and the defendant is called upon for an explanation. If he produces no satisfactory explanation, negligence is presumed against him, because the accident is one which usually does not occur where care is exercised.