'The process made me do it, Your Honour' may not be the best defence line in a court of law but it's nearly always true when errors occur in business processes. Human beings are fallible but the processes that they use should not allow those errors to occur.
In LEAN this is known as error proofing and should be built in to every process design or improvement. Some errors can be easily predicted and prevented but others may need a Failure Mode and Effect Analysis (FMEA) to discover the potential unknowns.
Since the cost of an error can be vastly greater than the cost of prevention in the first place, it's always worth stepping through a process, either in reality or virtually, before letting those unpredictable and innovative human beings break it and when they do, continually incorporating additional error proofing. This level of scrutiny is frequent in many industries, especially where safety is at stake, but common business processes are often forgotten.
So make 'What could possibly go wrong?' the first question you ask.