**Core Concept**
The McNaughton rule is a legal precedent that determines the test for criminal responsibility in cases of mental disorder. It is a key concept in forensic psychiatry, used to assess whether an individual was legally responsible for their actions at the time of the offense.

**Why the Correct Answer is Right**
The McNaughton rule states that "to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or, if he did know it, that he did not know he was doing what was wrong." This means that the defendant must have been suffering from a mental disorder that impaired their ability to understand the consequences of their actions. The McNaughton rule is still widely used today to determine criminal responsibility in cases where mental illness is a factor.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately reflect the McNaughton rule. While the rule does involve a consideration of the defendant's mental state, it is not simply a matter of whether they were "insane" at the time of the offense.

**Option B:** This option is incorrect because it inverts the burden of proof. Under the McNaughton rule, it is the prosecution that must prove the defendant was criminally responsible, not the defendant who must prove they were insane.

**Option C:** This option is incorrect because it is too broad. The McNaughton rule is a specific legal precedent that applies only to cases of mental disorder, not to all criminal defenses.

**Clinical Pearl / High-Yield Fact**
The McNaughton rule is often remembered using the mnemonic "Did he know what he was doing was wrong?" This helps clinicians to recall the key elements of the rule and to apply it in cases where mental illness is a factor.

**Correct Answer:** D. The McNaughton rule is a legal precedent that determines the test for criminal responsibility in cases of mental disorder.