Just finished watching a very good programme on the JFK assassination on BBC2.
The conclusion was two-fold:
1. Lee Harvey Oswald definitely shot and killed JFK.
2. He acted alone.
From the programme a few things transpired (and yes, I know you shouldn't believe everything you see on TV):
1. Oswald was a very good shot. In the USMC he regularly attained 48-49/50 in practices of 200 yds rapid. The distance from his position to JFK was 80 yds. It was also well within his ability to fire off 3 shots in the 8.3 seconds that he did so.
2. The first shot that hit JFK and Governor... errr... (sorry forgot the Governors name

) came directly from the 6th floor window that Oswald occupied. Its trajectory was exactly correct for it to pass through JFK and the governor sitting in front of him.
3. The bullets that hit JFK and the Governor were fired from Oswalds rifle.
4. The second shot that hit JFK (head shot) could not have been fired from in front of the car. It could only have been fired from the rear and at an elevated angle.
So in short there was no conspiracy or a gunman on the grassy knoll. There was much evidence to support the fact that Oswald acted alone, but this post has gone on for long enough already.