From the FBI (freedom of information act) the following
document was released to a history professor (and Lennon
family friend) at San Francisco State University. 
The 'smoking gun' is the paragraph which reads: 

   Wildes said Sen. Strom Thurmond, R-S.C., sent a letter
to Mitchell in February 1972, enclosing the committee 
memorandum.
    "This appears to me to be an important matter, and I
think it would be well to be considered at the highest
level...as I can see many headaches might be avoided if
appropriate action be taken in time," Wildes quoted
Thurmond's letter as saying.


    AND NOW YOU KNOW.