Case Facts
The Crown issued a government proclamation offering a reward of £1,000 to any person who provided information leading to the arrest and conviction of the person or persons responsible for the murders of two police officers, Walsh and Pitman. Clarke, who had himself been arrested alongside a man named Treffene on a charge of murder, subsequently gave information to the police concerning those murders. Crucially, however, Clarke gave this information not in response to the proclamation, but exclusively to clear his own name and extricate himself from the murder charge he was facing. Clarke later brought a petition of right under the Crown Suits Act 1898 (Western Australia), claiming entitlement to the £1,000 reward.
At first instance, McMillan CJ gave judgement for the Crown. The Full Court of Western Australia, by majority, reversed that decision and found in Clarke's favour, relying in large part on Williams v Carwardine (1833). The Crown appealed to the High Court of Australia.
Held
The High Court of Australia allowed the Crown's appeal and restored the judgement of the trial judge, holding that Clarke was entitled to neither the reward nor any moral claim to it. Clarke had not acted in reliance upon or in response to the proclamation when he gave the information to the police. Because his sole motivation was to clear himself of the murder charge, there was no valid acceptance of the Crown's unilateral offer, and accordingly no contract came into existence.
Ratio Decidendi
The central principle established by the decision is that, even in the context of a unilateral contract, acceptance is just as essential as offer. For a valid acceptance of a unilateral offer to arise, the act of performance must be done by a person who acts upon, in pursuance of, in reliance upon, or in return for the offer. It is not sufficient that the person merely performs the precise act described in the offer if that act is carried out for entirely independent reasons unconnected to the offer itself.
The court drew a clear distinction between the objective and subjective dimensions of acceptance in this context. A person may be entitled to a reward even if they are motivated partly by other considerations — such as conscience or personal feeling — provided they had knowledge of the offer and acted in response to it. This was how Williams v Carwardine (1833) was distinguished: in that case, it could be inferred that the claimant had knowledge of the reward and acted in response to it, even though she was additionally motivated by a troubled conscience. Clarke's situation was fundamentally different: he had known of the proclamation at some point but had put it entirely out of his mind, and when he gave the information he was acting solely on his own initiative and for his own protection.
The court rejected the proposition that performance of the requested act is automatically sufficient for acceptance merely because the act corresponds in its description to what the offer specified. As the court stated, it is not true to say that since such an offer calls for information of a certain description, then, provided only information of that description is in fact given, the informant is entitled to the reward. Performance must be given in exchange for the offer — that is, it must be the offer that moves the offeree to act.
The decision also drew support from Carlill v Carbolic Smoke Ball Company [1893], which had established that performance of the conditions stipulated in a unilateral offer constitutes the mode of acceptance. The court emphasised, however, that this principle presupposes that the person performing the conditions does so by acting upon the offer — that is, in reliance on it. Performing the conditions without any awareness of or reference to the offer cannot constitute acceptance.
In summary, three requirements flow from this decision for the acceptance of a unilateral offer:
- The offeree must have knowledge of the offer at the time of performing the requested act.
- The offeree must perform the requested act in response to the offer — that is, the offer must be the reason, or at least a reason, for the act.
- The act of performance must not be entirely disconnected from the offer; where the offeree performs the act solely for reasons of personal self-interest unrelated to the offer, no acceptance arises.
Obiter Dicta
The court confirmed, by way of broader principle, that an act done in complete ignorance of an offer cannot constitute acceptance of that offer. A person who performs the requested act without any awareness of the offer's existence — or who, having once known of it, has entirely forgotten it by the time they act — cannot be said to have accepted it. This obiter observation reinforces the fundamental requirement of knowledge as a precondition to acceptance in the law of unilateral contracts. The principle applies regardless of whether the act performed objectively satisfies the terms of the offer, since acceptance requires a meeting of minds directed towards the same transaction, not merely a coincidence of conduct.