R v Hennessy [1989]

1. Facts:

• D, a diabetic, was found driving a stolen car while in a state of hyperglycaemia (high blood sugar).

• Failed to take insulin due to stress and depression.

2. Outcome:

• D was found not guilty by reason of insanity.

• The court held that hyperglycaemia, caused by the underlying diabetes and failure to take insulin, was an internal factor.

3. Impact and Analysis:

• Internal Cause: Established that hyperglycaemia is considered an internal factor under the McNaughton rules.

• Mental Illness: Emphasised that stress and depression are internal causes, reinforcing the scope of conditions considered for the insanity defence.