A rather poor safety net that is often used by the guilty when they testify before congress. The degree to which the testifier uses this phrase often indicates how much they have to hide. This phrase was recently made famous by Alberto Gonzales when he testified in April of 2007.
Alberto Gonzales used the old "I don't recall" trick 71 times when he testified before congress the other day. That means he's really guilty or really stupid. Most likely both.