For FAA the standards are clearly written down, and the AME's have a thick manual to follow. Obviously those standards vary with Class 1,2, or 3.
If the AME fails to examine and document to those standards he/she won't last long in the job. That doesn't mean that there aren't some who won't take their responsibility seriously. In most cases the pay for the work does not cover expenses.
I doubt that things are different for CAA/JAA.