Understanding the ‘fault’ in prior-fault intoxication: insights from behavioural neuroscience

Intoxication is commonly associated with disinhibition and criminal conduct, where a defendant’s (D’s) claim that she ‘only did it because of the drugs’ is a matter for sentencing. But where D’s intoxication is acute, it can sometimes result in D causing potentially criminal harms without mens rea; and D’s claim changes to ‘because of the drugs, I didn’t know what I was doing’. Here, D’s claim is a matter for liability: if D lacked essential mens rea, then she did not prima facie commit an offence. Prior-fault intoxication rules apply here, at the liability stage, to expand the legal evaluation of D’s conduct to include both actions in becoming intoxicated as well as actions when later causing harm, using this expanded lens to criminalise D as if she had mens rea.

In this chapter we examine the intoxication rules, focusing on the ‘fault’ identified within such rules as a substitute for D’s missing mens rea; using insights from the fields of behavioural and neural science. Scientific enquiry into mens rea states has some academic history, exploring how people experience and process mens rea states, whether juries understand directions on mens rea, and so on. But neuroscientific enquiry into prior-fault intoxication is different, and potentially highly significant, looking to construct a picture of exactly what the criminal law is targeting as fault.