There are way too many improprities in this story to attribute to 'an honest mistake'. People like Berger, a highly successful attorney and former Presidential Advisor on National Security, simply do not take notes of highly classified documents and stuff them in their pockets and go home, knowing full-well that this is illegal. They also aren't likely to "mix up" these top secret documents with non-classifed stuff in their briefcase.
Nobody believes Berger's story, but the liberals will work feverishly to cover his behind. For them, the security of America plays second banana to implementing the liberal agenda.