He has held visiting appointments in criminology at Oxford, Sydney, Griffith and Cambridge, in psychology at New York University and John Jay College of Criminal Justice, in law at Yale, and in public policy at Harvard (Kennedy School).
Working at the intersection of psychology and law, his research focuses on procedural justice (the importance of fair process in interactions between power-holders and subordinates), distributive justice (the allocation of finite resources that determine who gets the benefits and burdens of social control)and legitimacy (perceptions of the right to power) in the context of the criminal justice system. He is interested in clarifying the meaning and measurement of these concepts; understanding the causal mechanisms that transmit the effects of procedural justice, distributive justice and legitimacy on various behavioural and attitudinal outcomes; testing how well procedural justice theory travels across diverse social, political and legal contexts using methodologically equivalent research designs; bringing perceptions of structural racism into procedural justice theory; and examining the importance of ‘bounded authority’, i.e. respecting the limits of one’s rightful authority.