'Shyster' is described by its developer, Dr James Popple, as a A Pragmatic Legal Expert System. Whilst it produces useful results, it does so using a very different process to that which a barrister might. ‘Shyster’, like all Legal Expert Systems uses a mechanical reasoning process and can never include the qualitative dimension of a barrister’s reasoning process.

Mycin was one of the earliest examples of an expert system, developed in the early 1970’s at Stanford University for the purpose of diagnosing and proposing courses of treatment for blood infections. The medical expert system represented its knowledge in the form of IF-THEN statements coupled with factors of certainty. These certainty factors are less relevant in the context of legal expert systems where answers tend to adhere to the black and white.

Shyster-Mycin is a hybrid legal expert system developed by Tom O’Callaghan that combines Shyster and Mycin. It combines rule-based reasoning for the treatment of legislation with case-based reasoning to explain concepts encountered in legislation.