Assists are the most subjective of stats. The key point on awarding an assist is that it needs to appear as part of the play or be a pass that prompted the shot.
This is the full published philosophy on awarding assists in mens lacrosse: An assist is not necessarily credited to a player who makes a pass before a goal. There should be conscious effort on the part of the passer to find an open player for a shot or to help a player work free for a shot. There should be no particular time frame for an assist (although the pass and shot should appear to be part of the same play) nor should there be any rigid distance factor in the play (the player scoring the goal could take one step, several steps, or even run a number of yards with the ball and still have the passer credited with an assist). An assist should not be credited on a play when the goal scorer dodges a defensive player after receiving the pass before shooting unless, in the opinion of the statistician, it was the pass itself and not the dodge that led directly to the shot.