Yes and yes.
Eyewitness testimony exists from both sides that places the shot on the American side of the green amongst the militia, the British side of the green amongst the militia, or not on the green at all and amonst some of the militia that was still streaming in from outside Lexington proper.
"As the one shot rang out, the British infantry line began to fire in earnest."
That infers that the British were firing BEFORE the single shot. Not the case at all. After the single shot it is agreed to by all sides that the British regulars, acting to their training, went into autopilot and began firing.
Yes, I've heard the theory that Lt. Sutherland fired the first shot accidentally. That's also highly disputed. There were numerous British regular witnesses who said that the first shot was fired, accidentally or on purpose, that's not clear, by a an American crouched behind a wall off the green.
Finally, others claim that there were scattered shots from BOTH sides prior to the "Shot heard round the world," but that is soundly refuted by any number of British regulars in official depositions, while depositions from Americans in the militia unit claim that they were fired on first.
In essence, it's the grassy knoll of the American Revolution, with more than enough claims and theories flying around.
That I simply