Mark David Chapman's first statement to the police after shooting Lennon was "I acted alone". He's repeated that over and over. "I acted alone".
Lennon was #1 on Nixon's "Enemies" list.
Nixon tried to have him deported in a case that went all the way to the Supreme Court (they said no 7-2).
To this day the FBI refuses to release 10 pages of their files on Lennon, a case closed in--yep 1981.
If you wern't around then you can have no idea of the infulence he had with the big bulge in the demographics (Boomers). He had unlimited cash, and in the pre-cable/soma days, everything he said and did was News. The Concert for Bangladesh was the First global relief attempt of it's type and it's political ramafications were not lost on the corportatists.
Summation:
Smells like a hit. Looks like a hit. Was it a hit? I donno. Release those ten pages and see if they tell the tale.
Addenum:
Chapman's up for parole on '06.