> Did these guards sleep more than guards at other prisons?

No idea.

It just seems a poor defence of the events of that particular night by also stating that it's a common problem.

I'm not defending the events, I'm trying to establish whether or not they are anomalous.

I didn't mean that you were defending anything. I just think that the various events are indicative of problems whether or not they are anomalous.

As a bad analogy, if a murder suspect was found to be carrying an illegal weapon on the night in question, it would hardly work in their defence for them to state they often carried an illegal weapon.