Knightley v Johns [1982] 1 W.L.R. 349
Facts
A motorist drove his car down a tunnel, and at a sharp bend the car somersaulted and came to rest overturned with the motorist inside it, blocking the right-hand lane. C, a police constable, rode out the northern end of the tunnel and radioed for ambulances and a fire engine. C went back into the tunnel to meet with other policemen on the scene. The inspector, D, had forgotten to seal off the tunnel at the other end and told another policeman and C to do so. C followed this other policeman headed down the tunnel the wrong way. An oncoming car swerved to avoid the first policeman, colliding with C.
Legal Issue
Did the negligent driver's original obstruction remain a legal cause of the constable's injuries, or did the inspector's subsequent orders break the chain of causation?
Held
The Court of Appeal held that the inspector's negligent intervention broke the chain of causation between the original driver's negligence and the constable's injuries. The driver had created an emergency by obstructing the tunnel, but the inspector then failed to close the tunnel and ordered officers to ride against the traffic. These were positive acts introducing a fresh danger, rather than an ordinary consequence of dealing with the initial obstruction. The court did not suggest that every error by a rescuer or police officer breaks the chain. Its conclusion depended on the character and sequence of the inspector's mistakes, which made this an independent cause of the later collision.
⭐ Legal Principle
A negligent intervention can break the chain of causation where it introduces a sufficiently independent danger. Ordinary rescue mistakes may remain foreseeable consequences of the original wrong, but the inspector's exceptional sequence of negligent orders in Knightley constituted a new intervening cause.
Significance
Knightley helps distinguish factual involvement from continuing legal responsibility. The original crash explained why the officers attended, but that did not make the driver liable for every later accident. Compare ordinary rescue cases, where responding to a danger normally falls within the original risk. In a problem question, identify the precise intervention, the danger it introduced and whether it was an expected incident of managing the emergency. Do not treat the mere presence of another negligent defendant as decisive.
Common exam questions about this case
Why was the original driver not liable for the constable's later injuries?
The driver's negligence brought the police to the tunnel, but the inspector subsequently created a distinct danger by directing officers against oncoming traffic without closing the tunnel. The court treated that exceptional intervention as breaking the legal chain. Being a factual starting point was insufficient for continuing liability.
Does negligent police conduct invariably break causation?
No. Knightley turns on the particular intervention and the danger it created. Some mistakes are foreseeable incidents of rescue or emergency management and leave the original defendant responsible. The examiner expects analysis of the sequence and seriousness of the intervention, rather than a rule that subsequent negligence automatically ends liability.
How would you distinguish an ordinary rescue response?
An ordinary rescue response is directed at the danger already created and may involve predictable errors under pressure. In Knightley, the inspector's orders introduced a new collision risk through a combination of procedural failures. The distinction concerns the independence and character of the intervention, not whether the person intervening intended to help.