Seriously! Do you think that background checks involve interviewing everybody in your past. Especially for secret clearances. You get to pretty much hand pick who gets interviewed for TS by putting it on you SF86. I got a TS while my DL was suspended(this was in the 90's). I recieved my clearance and a week later recieved a letter from my home town telling I missed a court appearance for a ticket I thought i paid off. Was I a murderer...no, but the investigation process isn't foolproof. Some bases use E-verify for civilian workers that come in for a project or construction. Snowden, from what I've read had a perfect background with no problems. Not sure what happened with Alexis. There are a lot of military that get cleared for S/TS/SCI that have skeletons in their closet and only after the fact that issues come to light.