The Future of Freedom Foundation:
One of the most common lies in the criminal-justice system is the I dont remember lie. The reason people use it is that they know that it is extremely difficult to prove that the statement is, in fact, a lie that is, that the person really does remember the event, contrary to his representation. One of the reasons the feds were able to successfully pin the charge on Martha Stewart was that the conversation she supposedly didnt remember was “too important” to have been forgotten.
Thanks to Matt Mower of eVectors for the link