As a statistical organization we actually don't make that determination or judgment as to when an error occurred, or if an error occurred. We rely on the institutions who supply us with data to make that determination prior to giving us the data.
Certainly we want to look at contributing factors. The goal with those is to look at things within the system that we can modify to make the system safer. We don't make the determination of when an error occurred; we collect the data around that error to be able to inform on preventative strategies.