[MUSIC] [MUSIC] Just over 50 years ago, U.S. President John F. Kennedy was assassinated. He was shot and he was shot by a man called Lee Harvey Oswald. Since the assassination, many, many theories have gone round about what really happened on that fateful day, and we will probably never convince everybody of what really happened. One of the questions which never seems to go away is, did Lee Harvey Oswald act alone, or was there a second gunman who fired at the President? Well, maybe a little bit of elemental analysis can cast some light on this question. Now, how many bullets were fired by Lee Harvey Oswald? He fired three times. One shot completely missed the Presidential limousine. Two shots hit the Presidential limousine. So, what we should be able to do is to examine the car and see how many bullets are found. And if there is another gunman, then we would find more than two bullets. It's not that simple. Bullets can fragment. They can break up into parts when they hit the target. So when this crime scene was searched, they didn't find two bullets. They found all sorts of fragments of bullets. And now, the question is, how can we put these fragments together and work out the total number of bullets? It's not a jigsaw puzzle where you can just fit them together and see if they go together, because they deform. And so, they can't be just put back together. We need to use some chemistry, some elemental analysis. Of course, the bullets are made of lead, they're all made of lead. So, we're not interested in the bulk composition. What we're using is the trace element composition, and particularly two of the common trace elements in this kind of bullet, which are silver and antimony. Now, there were multiple fragments found and these have been grouped into five. And you can see that the level of silver in these five fragment groups is about the same. It varies from the low of 7.9 ppm up to a high of 9.8 ppm, not terribly much different. But, if you look at the antimony concentration, we find a bigger difference. There's two groups which have higher levels of antimony, about 800 ppm of antimony; and then we have another group, which have only about 600 ppm of antimony. So the most likely conclusion here is that fragment groups one and two come from the same bullet, which has the higher level of antimony. The other fragment groups three, four and five, come from another bullet which has this lower level of antimony. Because we can divide all these fragments into these two groups, the high level of antimony and the low level of antimony, it appears that there are only two bullets that hit the limousine, and this corresponds to the two bullets that Lee Harvey Oswald fired that hit the limousine. Well, it doesn't really prove there was only a single gunman, but it does not give any evidence that there was a second gunman. So, the conclusion of the investigation was that it most likely was a single gunman, Lee Harvey Oswald.