I've never been much of a Kennedy assassination conspiracy theory fan. It has generally seemed to me that Oswald as the lone assassin was as good a theory as most of the others that whirled around the tragedy, fitting most of the known facts.
However, this story is enough at least to make me wonder. Former FBI lab metallurgist William Tobin and a couple of Texas A&M researchers have raised the possibility of a third bullet, which would likely mean a second shooter, though they didn't weigh in on that.
The background. After retiringTobin questioned the science that had been used by the FBI to match bullets to crime suspects through their lead content. The National Academy of Sciences reviewed the topic and agreed in 2003 that the long-time FBI methodology was flawed. The FBI agreed and adopted the new recommended methodology. Tobin and the othefs then used the new methodology to analyze the five Kennedy bullet fragments, and concluded that they could have come from three bullets.
This doesn't strike me as conclusive yet, but as worthy of further scientific investigation.