Foetal alcohol spectrum disorders (FASD), and inadequate legal responses to FASD associated impairments, are a critical factor in the complex web of issues responsible for the over-representation of Aboriginal persons in the criminal legal system. In Western Australia (WA), one such inadequate response is the potential for indefinite detention of Aboriginal persons with FASD found unfit to stand trial. This article proposes the optimal realisation of principles underlying the doctrine of fitness to stand trial through a needs-based' approach. FASD is a symptom and legacy of colonisation. Consequently, a response to Aboriginal persons with FASD must address two needs: the needs' of persons affected by FASD, and the need' for decolonisation. This article uses emergent research on jurisdiction to analyse colonial criminal legal systems through a jurisdictional lens, and identifies opportunities for decoloniality through the creation of engagement spaces' between Aboriginal laws and non-Aboriginal laws. The emergence of such spaces is posited in the Kimberley region of WA. Ultimately, this article proposes a disposal for unfit Aboriginal persons with FASD that realises a needs-based' approach.