Partial Defences

Introduction

This chapter completes the study of general defences by examining the four doctrines that go to the defendant's **capacity to form mens rea or to control his physical conduct**: **insanity**, **automatism**, **intoxication** and **mistake**. These are **excuses** rather than justifications — they accept that the actus reus has occurred but argue that the defendant should not be held criminally responsible. The structural difficulty, and the reason this topic is so heavily examined in **FLK2**, is that English law treats different causes of incapacity in radically different ways: **insanity** is governed by the **M'Naghten Rules (1843)**, **automatism** is reserved for involuntary conduct caused by an **external** factor, **intoxication** distinguishes **voluntary from involuntary** and **basic from specific intent** under **DPP v Majewski [1977] AC 443**, and **mistake** is in truth a denial of mens rea under **DPP v Morgan [1976] AC 182**.

Assessment focus

For SQE1 FLK2 you must be able to **classify** the cause of a defendant's impaired capacity and apply the correct doctrine. The most heavily tested rule is the **Majewski** basic/specific intent distinction for voluntary intoxication; you must know which common offences fall on each side of the line. You should also master the **internal/external distinction** that separates insanity from automatism (**R v Quick; R v Hennessy**), the **special verdict** consequences of insanity, the **Kingston** limit on involuntary intoxication, the **Bailey** rules on self-induced automatism, and the **O'Grady / s. 76(5) CJIA 2008** rule excluding drunken mistakes in self-defence. Questions are single best answer (SBAQ) set in realistic scenarios; you must **apply** the rules and reach the correct outcome (acquittal, special verdict, imputed mens rea or conviction). This is a closed-book assessment.

Study tips

1) Learn the **four-step sequence** for any impaired-capacity problem: (i) identify the cause; (ii) classify the defence; (iii) classify the offence as basic or specific intent; (iv) apply the rule and state the consequence. 2) Memorise the **internal/external table**: epilepsy (**Sullivan**), sleepwalking (**Burgess**) and diabetic **hyperglycaemia** (**Hennessy**) = insanity (internal); **hypoglycaemia** from insulin (**Quick**) = automatism (external). 3) Memorise the **specific v basic intent lists** for Majewski. 4) Remember **'a drunken intent is still an intent'** (**Sheehan and Moore**) and **'a drugged intent is still an intent'** (**Kingston**). 5) Note that **murder is a specific intent offence** so very drunk killers usually drop to **unlawful act manslaughter** (basic intent). 6) Remember that **O'Grady / s. 76(5)** excludes drunken mistakes in self-defence on **both** basic and specific intent offences.