I don't care about the 'he said, she said' game, and nobody else should either. Fact is, there's a chain of responsibility, and everybody all up and down that chain is responsible for what happened. That's what it means to be in charge of people. You're responsible for what they do. And if they didn't do what was needed, then you've failed in you responsibility, even if at the time you thought you had information that indicated you were doing the right thing.