📚 Formula and Principle Quick Reference for A-Level WJEC Law | A-Level WJEC 法律：公式定理速查手册
In A-Level WJEC Law, you won’t find mathematical equations, but legal reasoning relies on structured ‘formulae’ – tests, principles and rules that consistently determine liability, guilt or the formation of contracts. This quick reference handbook brings together the most essential legal ‘formulae’ from Criminal Law, Tort Law and Contract Law. Each entry presents a simplified statement of the rule, followed by clear bilingual explanations to support your revision.
在 A-Level WJEC 法律中，虽然找不到数学方程式，但法律推理依赖结构化的“公式”——那些始终如一地决定责任、罪责或合同成立的检验标准、原则和规则。这本速查手册汇集了刑法、侵权法和合同法中最关键的法律“公式”。每个条目先用简化形式陈述规则，再用清晰的双语解释辅助你的复习。
1. Criminal Liability Formula | 刑事责任公式
Actus Reus + Mens Rea – Defence = Criminal Liability
In almost every criminal offence, the prosecution must prove beyond reasonable doubt that the defendant committed the guilty act (actus reus) while possessing the required guilty mind (mens rea), and that no valid defence exists. This equation is the bedrock of criminal law.
在几乎所有刑事犯罪中，控方必须排除合理怀疑地证明被告实施了犯罪行为（actus reus）并具有必要的犯意（mens rea），且不存在有效的抗辩。这个方程式是刑法的基石。
The actus reus must be a voluntary act; an omission only counts where the defendant owed a legal duty to act – for example, a statutory duty, contractual obligation, or a special relationship such as parent and child.
犯罪行为必须是自愿行为；不作为只有在被告负有法律作为义务时才成立，例如法定义务、合同义务或父母与子女这类的特殊关系。
Mens rea ranges from direct intention and oblique intention to recklessness and negligence. Strict liability crimes are the exception, requiring no mens rea at all. Always check whether the defendant can raise a complete or partial defence, such as self-defence, automatism or diminished responsibility.
犯意涵盖直接故意、间接故意、轻率及过失。严格责任犯罪是例外，完全不要求犯意。务必考虑被告是否能提出完全或部分抗辩，例如自我防卫、无意识行为或减轻责任。
2. Caparo Three-Stage Test for Duty of Care | 卡帕罗三步检验法（注意义务）
Foreseeability + Proximity + ‘Fair, Just and Reasonable’ = Duty of Care
The modern test for establishing a duty of care in negligence comes from Caparo Industries plc v Dickman [1990]. The court will impose a duty only if three elements are satisfied: the harm was reasonably foreseeable, there was sufficient proximity between claimant and defendant, and it is fair, just and reasonable to impose liability.
现代过失侵权中确立注意义务的检验标准源自Caparo Industries plc v Dickman [1990]。法院仅在三个要件都满足时才认定注意义务：损害具有合理可预见性、原告与被告之间存在充分的邻近关系，并且施加责任是公平、公正且合理的。
Foreseeability asks whether a reasonable person in the defendant’s position would have foreseen that the claimant could be injured. Proximity covers the legal and physical closeness between the parties. The final ‘policy’ limb prevents the courts from extending liability too widely. This formula is particularly helpful for novel situations where no precedent duty exists.
可预见性询问处于被告位置的理性人是否会预见到原告可能受伤。邻近性涵盖当事人之间的法律与事实密切程度。最后的“政策”要件防止法院过度扩大责任范围。当面对没有先例注意义务的新型情境时，这个公式格外有用。
3. Contract Formation: Agreement Equation | 合同成立：协议等式
Offer + Acceptance = Agreement
Every contract begins with an agreement, which is broken down into a clear offer by one party and an unconditional acceptance by the other. The offer must be a definite expression of willingness to be bound on specific terms, distinguished from an invitation to treat.
每一份合同都始于协议，协议可分解为一方明确的要约和另一方无条件的承诺。要约必须是愿意受特定条款约束的确定表示，要与要约邀请区分开来。
Acceptance must mirror the terms of the offer absolutely (the ‘mirror image’ rule) and be communicated to the offeror. An important exception is the postal rule, established in Adams v Lindsell [1818]: where acceptance by post is contemplated, acceptance is complete as soon as the letter is posted, not when it is received.
承诺必须完全镜像要约的条款（镜像规则），并且传递至要约人。一个重要例外是邮政规则，由Adams v Lindsell [1818]确立：在可预见的邮寄承诺情境下，信件一经投递，承诺即告完成，而非到达时才生效。
Together, a valid offer and a valid acceptance create the agreement, which is the first essential ingredient of a binding contract. The other requirements are consideration, intention to create legal relations, and certainty of terms.
有效的要约和有效的承诺共同构成协议，这是一份具有约束力合同的第一项必备要素。其他要求还包括对价、建立法律关系的意图和条款的确定性。
4. Consideration Formula | 对价公式
Consideration = A Benefit to the Promisor OR a Detriment to the Promisee
Consideration is the price for which the promise is bought. The classic definition from Currie v Misa [1875] states that consideration consists of some right, interest, profit or benefit accruing to one party, or some forbearance, detriment, loss or responsibility undertaken by the other.
对价是换取承诺的代价。Currie v Misa [1875]中的经典定义指出，对价由一方获得的某些权利、利益、利润或好处构成，或者由另一方承受的某些克制、损害、损失或责任构成。
Four key rules govern consideration: it must move from the promisee, it need not be adequate but must be sufficient in the eyes of the law, past consideration is not good consideration, and performance of an existing duty generally does not amount to fresh consideration unless a practical benefit is conferred (Williams v Roffey Bros [1991]). Use this formula to check whether a promise is enforceable.
对价受四项关键规则支配：对价必须来自受诺人；对价无需相当，但必须在法律眼中具有充分性；过去的对价不是有效对价；履行既有义务一般不构成新的对价，除非被赋予了实际利益（Williams v Roffey Bros [1991]）。用这个公式检验承诺是否可强制执行。
5. Murder: The Ultimate Offence Formula | 谋杀罪：终极犯罪公式
Unlawful Killing + Malice Aforethought = Murder
Murder is a common law offence. The actus reus is the unlawful killing of a reasonable person in being under the King’s peace. The mens rea, known as malice aforethought, means an intention to kill or an intention to cause grievous bodily harm (GBH).
谋杀罪是普通法犯罪。其犯罪行为是对国王治下存活着的理性人实施非法杀害。犯意被称为恶意预谋，意指故意杀人或故意造成严重身体伤害（GBH）。
This formula is deceptively simple. Causation must be established: the defendant’s conduct must be both the factual (‘but for’) and legal cause of the death. A partial defence, such as diminished responsibility or loss of control, may reduce murder to voluntary manslaughter, but the core equation remains the starting point for any homicide analysis.
这个公式看似简单，实则复杂。必须确立因果关系：被告的行为必须构成受害人死亡的事实原因（“若无则不”检验）与法律原因。减轻责任或失控等部分抗辩可能将谋杀降为自愿误杀，但核心等式永远是分析任何杀人罪的出发点。
6. Intoxication Rule | 醉酒规则
Voluntary Intoxication ≠ Defence to Basic Intent Crimes
The principle from DPP v Majewski [1977] draws a crucial distinction. Voluntary intoxication can never be a defence to a crime of basic intent, where recklessness suffices for the mens rea. However, if the crime is one of specific intent, evidence of intoxication may be used to show that the defendant lacked the required intent.
DPP v Majewski [1977]确立的原则划出了一条关键分界线。自愿醉酒绝不能作为基本故意犯罪的抗辩，因为这类犯罪只需轻率即可满足犯意。然而，如果罪行属于特定故意犯罪，醉酒证据可用于证明被告缺乏必要的故意。
Basic intent offences include manslaughter, assault and battery. Specific intent offences include murder and theft. When you see a question involving a drunken defendant, immediately identify the type of intent required and apply this formula. Involuntary intoxication, on the other hand, can provide a full defence if it negates mens rea.
基本故意犯罪包括误杀、非法侵害和殴打。特定故意犯罪包括谋杀和盗窃。当你遇到醉酒被告的题目时，立即识别罪行的意图类型并应用这个公式。相比之下，非自愿醉酒若否定了犯意，可构成完整的抗辩事由。
7. Strict Liability Equation | 严格责任等式
Actus Reus Alone + No Valid Defence = Strict Liability
For regulatory and public safety offences, Parliament often imposes strict liability, meaning the prosecution does not need to prove mens rea for at least one element of the actus reus. The defendant can be convicted simply by committing the prohibited act, unless a statutory defence such as ‘due diligence’ applies.
对于监管与公共安全犯罪，议会经常施加严格责任，这意味着控方无需证明犯罪行为中至少一项要素的犯意。被告仅因实施了被禁止的行为即可定罪，除非存在“尽职调查”等法定抗辩。
Leading cases include Callow v Tillstone [1900] (selling unfit meat) and Harrow LBC v Shah [1999] (selling a lottery ticket to a minor). The courts look at the wording of the statute, the mischief it aims to prevent, and the severity of the penalty. Strict liability saves court time and promotes vigilance, but it can be harsh.
经典案例包括Callow v Tillstone [1900]（出售不合格肉类）和Harrow LBC v Shah [1999]（向未成年人出售彩票）。法院会考察法条用词、法条意图防止的恶害以及刑罚的严厉程度。严格责任节省司法时间并促进公众警惕，但也可能过于严苛。
8. Causation Formula in Result Crimes | 结果犯的因果关系公式
Factual Causation + Legal Causation = Causation
In result crimes like murder and manslaughter, the prosecution must prove a causal link between the defendant’s conduct and the prohibited result. The formula has two stages. Factual causation applies the ‘but for’ test: but for the defendant’s actions, would the result have occurred as it did?
在谋杀和误杀等结果犯中，控方必须证明被告行为与被禁止结果之间存在因果联系。该公式分两阶段。事实因果关系适用“若无则不”检验：若非被告的行为，结果是否仍会如此发生？
Legal causation requires the defendant’s conduct to be an operating and substantial cause of the result. It need not be the sole cause. An intervening act (novus actus interveniens) may break the chain of causation, but only if it is truly extraordinary and unforeseeable – for example, a victim’s refusal of life-saving treatment is generally not an intervening act.
法律因果关系要求被告的行为是结果的有效且实质原因，无需是唯一原因。介入行为（novus actus interveniens）可能中断因果链条，但前提是该介入行为真正异常且不可预见——例如，受害人拒绝接受救生治疗通常不构成介入行为。
9. Rylands v Fletcher Rule Formula | 瑞兰兹诉弗莱彻规则公式
Accumulation + Non-Natural Use + Escape + Damage = Strict Liability in Tort
The rule in Rylands v Fletcher [1868] imposes strict liability for damage caused by the escape of a dangerous thing accumulated on land in the course of a non-natural use. This is a tort of strict liability, meaning fault is irrelevant.
Rylands v Fletcher [1868]规则对因非自然使用土地过程中积聚的危险物逸出所造成的损害施加严格责任。这是一项严格责任侵权，意味着过错无关紧要。
Post-Transco plc v Stockport MBC [2003], the House of Lords emphasised that ‘non-natural use’ must be some extraordinary and exceptional use of land. The damage must also be reasonably foreseeable. Defences include consent, the act of a stranger, statutory authority and the claimant’s own default.
Transco plc v Stockport MBC [2003]之后，上议院强调“非自然使用”必须是对土地的某种极其特殊且例外的使用。损害还必须具有合理可预见性。抗辩事由包括原告同意、陌生人行为、法定授权以及原告自身过错。
10. Self-Defence Formula | 自我防卫公式
Honest Belief + Reasonable Force = Lawful Self-Defence
Self-defence is a complete defence in both criminal law and tort. Section 76 of the Criminal Justice and Immigration Act 2008 clarifies that a person may use such force as is reasonable in the circumstances as they honestly believe them to be. The test is subjective as to the defendant’s belief but objective as to the reasonableness of the force used.
自我防卫在刑法和侵权法中均为完全抗辩。《2008年刑事司法与移民法》第76条阐明，个人可以在其真诚相信的情境下使用在当时情形中合理的武力。检验标准在被告信念上采主观说，但在武力合理性上采客观说。
A pre-emptive strike can still be lawful, and the defendant is not expected to weigh to a nicety the exact measure of defensive action. However, if the force is disproportionate or retaliatory, the defence fails. This formula often appears in scenarios involving burglars or street confrontations.
先发制人的打击仍然可以是合法的，被告也无需精确权衡防卫行为的尺度。然而，若武力不成比例或具有报复性质，则抗辩不成立。这个公式常出现在涉及入室窃贼或街头对抗的情境中。
11. Joint Enterprise and Secondary Liability | 共同犯罪与从犯责任
Principal + Accessory with Foresight = Joint Liability
Under the Accessories and Abettors Act 1861, a person who aids, abets, counsels or procures the commission of an offence is liable as a secondary party. The modern approach from R v Jogee [2016] requires the accessory to have encouraged or assisted the principal, and to have intended to do so, with foresight of the possibility that the principal might commit the offence.
根据《1861年从犯与教唆犯法》，帮助、教唆、劝说或促成犯罪实施的人应作为从犯承担责任。R v Jogee [2016]确立的当代方法要求从犯必须鼓励或协助主犯，并且意图如此行事，同时预见到主犯可能会实施该犯罪的可能性。
Mere presence at the scene is insufficient; there must be active participation or encouragement. This formula is vital for analysing gang-related offences or group violence, where more than one person is involved in a criminal enterprise.
仅仅出现在现场是不够的；必须有积极的参与或鼓励。这个公式对于分析涉及多人的帮派犯罪或群体暴力至关重要。
12. Private Nuisance Equation | 私人妨害等式
Unreasonable Interference + Protected Land Interest = Nuisance
Private nuisance protects a person’s right to use and enjoy their land. The formula requires the claimant to prove an unreasonable interference with that right. Unreasonableness is assessed by balancing the competing interests of neighbours, taking into account factors such as duration, locality, sensitivity of the claimant, malice, and the social utility of the defendant’s activity.
私人妨害保护个人使用和享有土地的权利。该等式要求原告证明对该权利构成了不合理的干涉。不合理性是通过平衡相邻方利益来评估的，考量因素包括持续时间、地点、原告的敏感性、被告是否存在恶意以及被告活动的社会效用。
Physical damage to property is almost always unreasonable, whereas interference with comfort and amenity depends on the ‘give and take’ principle between neighbours. Remedies include damages and injunctions. This formula helps you structure problem questions on nuisance effectively.
对财产的物理损害几乎总是不合理的，而对舒适和便利的干涉则取决于邻里间“相互容让”原则。救济措施包括损害赔偿和禁令。这个等式能帮助你有条理地解答有关妨害的问题。
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