What limits to harmonising justice?

This chapter is concerned with how tradition and change affect differences between jurisdictions within the European Union (EU), where supranational legal structures and ideologies appear to leave little room for the ‘insider perspective’. The principles of mutual recognition and harmonisation of criminal law and procedure in Member States have created a legal sphere transcending the national. It presupposes a common legal order in which a shared conception of fair trial is the norm and provisions of substantive law are, if not identical, then at least totally compatible and based on common notions of harm. Whether or not harmonisation is desirable is not the issue here. My concern is with the assumptions that underlie an ongoing process and their effect on criminal justice in the national sphere. Can we assume a common legal order of criminal justice in which conceptions of fair trial and harmonised substantive law are shared across the European Union? Or do different social constructions and legal cultures at the national level (and the resulting supranational political compromise) pose limits to how far we can approach this purportedly ideal state of affairs? And, if that is the case, how do they make themselves felt and what are the consequences?