64. Inference of defendant's negligence.

Under the doctrine res ipsa loquitur1 a claimant establishes a prima facie case of negligence where:


    (1)     it is not possible for him to prove precisely what was the relevant act or omission which set in train the events leading to the accident; and


    (2)     on the evidence as it stands at the relevant time it is more likely than not that the effective cause of the accident was some act or omission of the defendant or of someone for whom the defendant is responsible, which act or omission constitutes a failure to take proper care for the claimant's