FBI is also on that list: http://www.browardbeat.com/broward-probe-302-reasons-not-to-...
"Federal agents have the right to lie to you-and to put you in prison if you lie to them. Any citizen who makes even a single-word false utterance (”no,” “yes”) to a federal agent faces up to five years in prison and a $250,000 fine." : http://jimbovard.com/blog/2010/08/18/the-crime-of-lying-to-t...
They try to make witnesses contradict themselves, so that they can invoke this law and scare them into testifying what they need to hear.