There are many theories available to criminologists to help explain, measure and attempt to understand criminal behaviour and the occurrence of crimes. This essay will take an in-depth look at one of these theories, the bio-behavioural reward dominance theory and seek to apply this to the case study of Edward ‘Ned’ Kelly, a noteworthy pre-federation Australian criminal, and his crime of murder. Firstly, it will cover the major components of the theory and how they are defined, as well as what, if any, major assumptions are taken. It will then identify the case study subject in more detail and expand on the unique bio-behavioural differences of Kelly that are attributed to increased criminal risk factors. This essay will draw evidence of these behavioural markers from both his early criminal activity and non-criminal activity and use empirical research to support the link of these bio-behavioural differences and criminal activity. It will then examine how these behavioural traits link to crime and explore the key crime committed under the lenses of reward dominance theory. Before concluding, this essay will evaluate the strengths and weaknesses of the reward dominance theory and discuss what possible shortcomings there might be. It will then conclude by summarising the bio-behavioural markers that show how reward dominance theory applies to Kelly’s act of committing murder.