Automatism Defence
Sometimes people act without conscious control - this is where automatism becomes relevant. Your actions must be completely involuntary to qualify for this defence.
There are two types: insane automatism (caused by a disease of the mind, which actually becomes an insanity defence) and non-insane automatism (caused by external factors like trauma or injury). The key difference matters because non-insane automatism leads to complete acquittal.
R v T (1990) perfectly illustrates this - a woman committed robbery whilst suffering PTSD after being raped. Since rape was an external factor, she could use non-insane automatism. Similarly, Hill v Baxter (1958) shows how sudden illness causing blackouts whilst driving can qualify.
However, self-induced automatism rarely works as a defence. If you know your actions might trigger an automatic state (like not taking prescribed medication), the courts won't be sympathetic.
Remember: External factors like head injuries, trauma, or sudden medical episodes can support automatism, but you can't rely on conditions you've caused yourself.