FBI suppressed exculpatory evidence in Leonard Peltier's trial - FBI firearms expert Evan Hodge lab notes showed the firing pin test did not match the casing from the RESMURS scene, but testified at trial that the test was "inconclusive".
http://whale.to/b/cointelpro_7.html
The COINTEL PAPERS by Ward Churchill and Jim Vander Wall
http://whale.to/b/wall_b1.html
Chapter 1 Understanding Deletions in FBI Documents
http://whale.to/b/wallch1.html