Tom Busey was the head of the NFA division at ATF. They are charged with keeping records for legally owned and registered machine guns. Some years ago he gave a speech where he rather cavalierly admitted that the NFA will tell the court what they want to hear. Here is an excerpt (transcribed by me) from the video (2.2 MB):

"Let me say that when we testify in court, we testify that the database is 100% accurate. That's what we testify to, and we'll always testify to that. As you probably well know, that may not be 100% true. If it was.. if our database was absolutely error free, we could simply run the name of the individual and his first name and it didn't come up, we could guarantee everyone that that individual doesn't have a title II weapon registered to him...

We know that you're basing your warrants on it, your basing your entries [entries = raids, like in Waco] on it and you certainly don't want a form 4 waved in your face when you go in there... I've heard that's happened."

What he's saying here is that he doesn't want to put the ATF into a position where they raid someones property expecting to find illegal firearms, only to find out that they are legally owned. He later admits that the error rate in the database was as high as 50%, but has fallen to 8%. But remember, they'll always testify in court that it's 100% accurate.

Personally I'm not at all surprised. I've had people tell me that the ATF has contacted them for a copy of their form 4 because the Bureau inadvertently lost their copy.

(Via David Hardy, Via Say Uncle)