In an action for damage arising from negligence the burden of proving negligence on the part of the Defendant lies on the Plaintiff.
In a civil action the standard of proof is on the balance of probabilities. In other words, the Plaintiff must prove that it is more likely than not that the damage was caused by the Defendantâs negligence. If the Plaintiff can go no further than to prove that the probabilities of negligence and no negligence on the part of the Defendant are equal, the Plaintiff will have failed to discharge the burden of proof and will lose.
Furthermore, if at the close of the Plaintiffâs case the Plaintiff has not adduced sufficient evidence of negligence on the part of the Defendant to be given a verdict (in the absence of evidence from the Defendant) the Plaintiff will have failed to discharge the burden of proof and will lose.
Where the Plaintiff has adduced a prima facie case of negligence against the Defendant, it is then incumbent on the Defendant to try to rebut the Plaintiffâs evidence. (The Defendant will have been busy during the presentation of the Plaintiffâs case trying to do exactly that. The means of doing so is cross-examination).
If the Defendant has not fatally undermined the Plaintiffâs evidence by cross-examination and at the close of the Plaintiffâs case there is a prima facie case (at least) to be answered, then it will be incumbent on the Defendant to adduce rebuttal evidence.
Now the Plaintiff will have the opportunity to try to undermine the Defendantâs evidence, again by cross-examination.
During this process the positions of the parties, in terms of reaching for and achieving success, will wax and correspondingly wane.
This was the context in which the judge in Byrne v Boadle (1863) 2 H & C 722 as he considered the evidence of the Plaintiff, that a barrel of flour fell on him from a window above the Defendantâs shop, told the Defendantâs barrister that âit would be wrong to lay down as a rule that in no case can presumption of negligence arise from the facts of an accidentâ?, and in so doing launched what became known as âres ipsa loquiturâ? (âthe thing speaks for itselfâ?).
The rule can have more than one meaning and courts in different jurisdictions have not adopted one and the same meaning. It can mean:
a) That the facts proved (the barrel of flour fell) warrant allowing the case to go to the finder of fact;
b) That the Defendant is obliged to show that it is equally probable that he was not negligent;
c) That the Defendant is obliged to prove he was not negligent;
In Ireland it is generally taken to mean c). This does not mean that the Defendant must prove how the accident happened; he must prove that he took all reasonable care.
In the case of Byrne v Boadle, the Plaintiff had no means of showing exactly why the barrel fell on him. The court took the view he did not have to; barrels are not known to jump from windows of their own accord and it was reasonable to infer that it fell due to an error of judgment or management of the occupier of the premises, the Defendant.
The cases decided by recourse to res ipsa loquitur show that the courts will only invoke the principle if the proved facts relate to relatively uncomplicated fields of human endeavour or where the general consensus in the field favours the inference of negligence on the part of the Defendant.
Consideration of the maxim clarifies the formidable burden of proof resting on Plaintiffs in some actions. The courts have shown that they are not ready to find for a Plaintiff unless the Plaintiff proves all the necessary elements of the claim in his/her evidence. If one of those elements is missing, evidence of the cause of the accident, say, the courts will not, on that account alone, require the Defendant to exculpate itself.
NOTE: There is a link above to Rothwell v Motor Insurers Bureau of Ireland. Because of the wording of the MIBI agreement the only issue before the court was negligence. In ordinary circumstances it would appear that the facts evidenced a public nuisance.