A decision of the Court of Appeal in which Megaw L.J. said, at page 755,
I doubt whether it is right to describe res ipsa loquitur as a `doctrine’. I think that it is no more than an exotic, although convenient, phrase to describe what is in essence no more than a common sense approach, not limited by technical rules, to the assessment of the effect of evidence in certain circumstances.
It means that a claimant] prima facie establishes negligence where
- 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; but
- (ii) 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 plaintiff’s safety.
I have used the words `evidence as it stands at the relevant time’ . I think that this can most conveniently be taken as being at the close of the [claimant’s] case.
On the assumption that a submission of no case is then made, would the evidence, as it then stands, enable the [claimant] to succeed because, although the precise cause of the accident cannot be established, the proper inference on the balance of probability is that that cause, whatever it may have been, involved a failure by the defendant to take due care for the [claimant’s] safety?
If so, res ipsa loquitur .
If not, the question still falls to be tested by the same criterion, but evidence for the defendant, given thereafter, may rebut the inference.
The res , which previously spoke for itself, may be silenced, or its voice may, on the whole of the evidence, become too weak or muted.
Paragraph broken up for ease of reading. See other cases listed under this tag especially Ratcliffe.