Epistemological Politics

The South Carolina AG announced, some time ago, that he absolutely, positively and without a shred of doubt KNEW that there were hundreds of people who voted dead in South Carolina. The Columbia Free Times reported:

S.C. GOP Attorney General Alan Wilson saying things like, “We know for a fact that there are deceased people whose identities are being used in elections in South Carolina.” - See more at: http://www.free-times.com/blogs/18-months-later-sc-law-enforcement-closes-case-on-zombie-voters-finds-no#sthash.z8MoGQJs.dpuf

The appropriate SC office - with the great name SLED - investigated. Did not find zombie voters.

My question is, in this case, what does it mean to "know" in a case like this. Can you "know" something that isn't the case? Is all knowledge subjective? If the objective "facts" turn out to not be the case that you asserted you "knew," did you not know what you said you knew? Does KNOWING require that you do something more than assert what you believe to be the case.

And if what you insisted you "knew" changes - i.e., you "knew" the mechanics of an evolutionary process and then someone else discovered that what you knew, what everyone knew, was not what was the case.

What does it mean to "know" something. And how do you come to know anything?