This paper reports on the theoretical and empirical developments for an error prediction methodology called task analysis for error identification (TAFEI). Other researchers have noted the need for theoretically driven approaches that are able to provide practical utility in error prediction. Theoretical developments include the concept of `rewritable routines', which describe the loop between cognitive processing, action and devices states. This has been proposed as a way of unifying ideas from systems theory and cognitive psychology. The empirical research shows that TAFEI is superior to heuristic methods, which supports the idea that structured methods assist in error prediction. The validation study shows that TAFEI reaches acceptable levels in terms of test-retest reliability and concurrent validity. It is believed that the method has reached a level of maturity after 10 years of development work. This is demonstrated by the many uses to which the method has been put, including that of a design tool.