The rule of external factor and internal factor was first expressed by Lawton LJ in the criminal case of R vs Quick  to distinguish between a defence of insane automatism (insanity) and a defence of sane automatism (automatism) 9, 10, 18, 34, 35. This test is widely considered in English criminal law and in some countries with the Anglo-Saxon legal system while arguing a case of automatism during judicial proceeding. If the incapacity results from an internal cause then the appropriate defence is insanity; if it is external, then it is a case of automatism 9,10,18, 31.
The external/internal test has been put forwarded on the basis of the recurrence theory or continuing danger theory 10, 24, 31. When an internal…show more content… It has been observed that often it makes illogical and hair splitting differences inevitable allowing some an outright acquittal while condemning others to plead guilty or take the risk of a special verdict 10. There is even less clarity in the correct legal approach where internal and external factors co-exist, for instance, sleepwalking, automatism in diabetic etc 39. A sleepwalker under the effect of dissociative confusional state may involve in automatic act and sometime may commit crime. The acute dissociative state, though internal problem in that particular individual, may result from some external factors such as ingestion of sedatives/ hypnotics including alcohol. In some cases, what starts as an external factor will eventually end up as internal one, for example Post traumatic stress disorder (internal factor) following rape (external factor) 40. From that point of view, defendant can be accused of sane automatism or insane automatism but subject to interpretation of law. Similarly, in cases of diabetes, a person might have either hyperglycaemia or hypoglycaemia and both states may be caused by “external factors” or “internal factors”. But law has been treating hypoglycemia and hyperglycemia differently in relation to automatism 10, 38. In the case of R vs Hennessy, the defendant had a hyperglycaemic episode caused by his failure to take a prescribed dose of insulin. His loss of control was created by a factor internal to him so his reliance on that at trial was classified as a plea of insanity 41. However, in the case of R vs Quick , the loss of control arose when the defendant suffered a hypoglycaemic attack following his failure to eat after taking insulin. His loss of control was considered to be resulted from