Although the general rules for negligence had been laid down by previous cases, Bolton v. Stone  AC 850 still gave the judges at the House of Lords some difficulty in deciding whether it constituted just such a case. As such, while upholding legal precedent, it also paved new grounds in some sense.
The facts of the case are as such: Miss Stone, the plaintiff, was on a side of residential houses when she was struck by a cricket ball hit by a player of a visiting team at the Cheetham Hill cricket ground. The ground was enclosed by a seven-foot fence, which actually stood seventeen feet above the pitch because the latter was sunk ten feet below the ground.
The wicket from which the ball was hit was about seventy-eight yards from the fence, and one hundred yards from the place of injury. According to a witness, Mr. Brownson, his house, which was on the same road but substantially nearer the ground than the place of injury, had been hit about six or seven times during the previous few years. Two members of the cricket club also agreed that the hit was exceptional, and that it was very rare for the ball to be hit over the fence between the road and the ground.
[...] Regarding policy implications, Bolton v. Stone clarified to what extent we have to take precautions against causing harm to others in our everyday activities within the context of an urbanised modern society, before being considered liable for negligence. [...]
[...] To answer the second question, the judges reasoned that the hit was entirely foreseeable, but unlikely. On top of this, however, another layer of probability was added: it is not enough that the event (the hit) can reasonably be foreseen; the further result that injury would occur had to be probable enough for a reasonable man to anticipate. (This compounding of probability—involving not only the exceptionality of the hit, but also this hit causing injury—was explicitly broken down only by Lord Porter.) Hence, because the risk of damage to a person on the road was infinitesimal, it was not necessary, to a reasonable man, to take precautions against such damage, since a reasonable man is liable only to try not to create a risk that is substantial. [...]
[...] Thus, since the hit that injured Miss Stone was exceptional, Bolton was not negligent. Similarly, they argued that the hitting of the ball into the highway was not actionable nuisance because nuisance is the continuance of a state of affairs, and not just an isolated instance—as was the case here since nobody had ever been injured before in this way in the ninety years that cricket had been played at Cheetham Hill. On the other hand, the main argument of Nelson, K.C., Henry Burton and Francis Clark for the respondent was that Bolton was negligent since it failed to take sufficient precaution to prevent the escape of cricket balls from the ground. [...]
[...] According to a witness, Mr. Brownson, his house, which was on the same road but substantially nearer the ground than the place of injury, had been hit about six or seven times during the previous few years. Two members of the cricket club also agreed that the hit was exceptional, and that it was very rare for the ball to be hit over the fence between the road and the ground. That Bolton v Stone reached the House of Lords in the first place indicates that it was a case of some contention. [...]
[...] Bolton v. Stone thus broke new ground by laying down the idea that a reasonable man would be justified in omitting to take precautions against causing an injury if the risk of the injury happening was very slight. This principle has been used in other cases, such as the The Wagon Mound (No  1 AC 617, where it was in turn weighed against the gravity of damage provoked. Oddly enough, Lord Reid seemed to have presaged this additional point of consideration in the deliberation of such a case when he remarked that would be right to take into account not only how remote is the chance that a person might be struck but also how serious the consequences are likely to be if a person is struck”. [...]
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