There isn't. There never was. Between 1967 and 1991, The Navy, the CIA, the Joint Chiefs, and numerous Senate and House committees have investigated the Liberty attack, and none of them have come to the conclusion that the ship was deliberately attacked by the Israelis. It happened because of bad communication on the part of the U.S. and major errors on the part of Israel. However, it was not intentional. It would never have happened if Israel weren't in the middle of the Six Day War. Does the phrase "The Fog of War" ring a bell?
It sure does, but does that now make them any less responsible?