Are there lessons to be learned from a more scientific approach to mental condition defences?

The timing of the English Law Commission's consideration of reform to the law of insanity coincides with increasing scientific and in particular neuroscientific understanding of the brain. The work of researchers is leading to a greater comprehension of what had been termed irresistible impulses to commit crime and of the impact of brain damage, particularly evidence of brain lesions and frontal lobe damage on behaviour. There remain problems in establishing causal relationships which might diminish or eliminate criminal responsibility for crimes committed by those suffering from pre existing mental conditions at the time they commit a criminal offence. This is especially the case where those mental conditions are of short duration. However, the law should not ignore the best available scientific knowledge. Neuroscientific advances are already informing court deliberations in England and Wales: assisting in considerations of guilt, fitness to plead and in sentencing. In terms of the insanity defence the questions that the law seeks to address are not necessarily the most medically or scientifically pertinent questions. They remain grounded in 19th century scientific understanding. It is argued that the more nuanced Dutch approach to mental condition defences warrants very serious consideration by those charged with making proposals to reform the English law.