Sirhan's gun held only 8 bullets. But the only tape of the assassination, examined by experts Spence Whitehead and Philip Van Praag, caused the experts to conclude more than 8 shots were fired.

Van Praag rules out the possibility that any of the 13 shots were echoes, ricochets or non-gunshot sounds. He also finds that some of the shots were fired too rapidly, at intervals too close together for all the shots to have come from Sirhan's inexpensive handgun. Van Praag further concludes that the five shots fired opposite the direction of Sirhan's eight shots displayed a "frequency anomaly" indicating the second gun's make and model were different from Sirhan's weapon.

Then there's the direction of the bullets:

[Sirhan's lawyer William] Pepper said that witnesses reported Sirhan was standing several feet in front of Kennedy and firing nearly horizontally while the medical evidence showed Kennedy's body and clothing were struck by four bullets fired point-blank from behind the Senator at steep upward angles.

Pepper also says it turns out Sirhan's trial lawyer, Grant Cooper, now dead, was under indictment:

Cooper was under federal indictment for illegally possessing grand jury minutes in an unrelated case, but the indictment was dropped after Sirhan's sentencing, Pepper said.

Who is Pepper? He says he not only knew the Kennedy family, but managed RFK's 1964 senate campaign for Westchester County. (Actually, he says here that he managed his "citizen's campaign" for Senate.) Pepper is an international human rights lawyer who also represented James Earl Ray for 10 years, alleging that MLK, Jr. was assassinated as part of "on-going covert program ...to suppress dissent and disruption in America" and Ray wasn't the shooter, just an "unknowing patsy." He represented the King family successfully in a civil lawsuit but the Justice Department disagrees.