6. Proving negligence: res ipsa loquitur

The Burden of Proof in Negligence

General rule: In ordinary civil claims, the burden of proof rests on the plaintiff. The plaintiff must show, on a balance of probabilities, that the defendant committed a specific breach of duty that caused the damage. If the plaintiff can only show that an accident took place, but cannot explain how or why it occurred, the claim will normally fail.

The exception: Sometimes, however, the circumstances surrounding an accident point so unmistakably to carelessness that the court does not need detailed evidence of what the defendant did or failed to do. In these exceptional situations, the common law applies the doctrine of res ipsa loquitur. This Latin phrase translates literally as 'the thing speaks for itself.'

The Definition of Res Ipsa Loquitur

The classic formulation: The classic test for the doctrine was laid down by Erle CJ in Scott v London and St Katherine Docks Co. He stated that where a thing is shown to be under the management of the defendant or their servants, and the accident is such as does not happen in the ordinary course of things if those in charge use proper care, it affords reasonable evidence, in the absence of an explanation, that the accident arose from a want of care.

Effect of the doctrine: When the doctrine applies, the mere happening of the accident tells its own story. It raises a prima facie inference of negligence, shifting the evidential burden to the defendant to offer a plausible explanation that does not involve their own carelessness. The story told by the facts must be clear and unambiguous.

Three Conditions for the Doctrine to Apply

The three requirements: For the court to draw an inference under res ipsa loquitur, the plaintiff must establish three distinct elements: first, the thing causing the harm was under the sole control of the defendant; second, the mishap is one that would not normally happen without negligence; and third, there is no direct evidence explaining why the accident occurred.

1. Sole Control by the Defendant

Control of vehicles: Whether the defendant had sufficient control over the instrument of damage is a question of fact in each case. Road traffic cases frequently provide examples. A motorist is presumed to have exclusive management of their vehicle, so when a car mounts the pavement and strikes a pedestrian from behind, as in Ellor v Selfridge & Co Ltd, the doctrine applies readily.

Continuous control required: Control must be real and continuous. In Easson v London and North Eastern Railway Co, a young boy fell through an open door on an express train between Edinburgh and London. The court held that the railway company did not have continuous, sole control over the door throughout such a long journey, because other passengers could easily have interfered with it.

Distinguishing railway cases: By contrast, in Gee v Metropolitan Railway Co, a passenger leaned against a train door that flew open just minutes after leaving the station. Because the train had only just departed under the direct supervision of the station staff, the railway company retained effective control, and negligence was properly inferred.

Vicarious liability: Where the thing causing the harm was managed by one of several employees of the defendant, the plaintiff does not need to identify the exact employee at fault. As long as the group as a whole was under the defendant's authority, the doctrine applies, and the employer can be held vicariously liable.

2. The Accident Would Not Normally Happen Without Carelessness

Falling objects: The mishap must be of a type that common human experience tells us does not occur unless someone was careless. Barrels and heavy sacks do not fall out of upper warehouse windows onto the street below if ordinary care is exercised, as demonstrated in Byrne v Boadle and Scott v London and St Katherine Docks Co.

Medical mishaps: The same reasoning applies in medical and surgical settings. For example, leaving a surgical swab or instrument inside a patient's abdomen after an operation, as occurred in Mahon v Osborne, is an event that does not happen in the ordinary course of careful medical practice, raising a strong inference of negligence.

3. Absence of an Explanation

No direct evidence needed: Res ipsa loquitur is a rule of necessity. It is used only when the plaintiff cannot prove the exact cause of the accident. If all the facts explaining how the accident occurred are already known to the court, the doctrine has no role to play, and the case must be decided on the direct evidence alone.

The Barkway principle: This limitation was demonstrated in Barkway v South Wales Transport Co Ltd. In that case, an omnibus suffered a burst tyre and crashed over an embankment. Because the evidence fully explained how the accident occurred—a defective tyre that should have been spotted during routine inspections—the court decided the case on proof of ordinary negligence, holding that res ipsa loquitur could not be relied upon.