Why did Lester frame his nephew in Fargo? As if it wasn't sociopathic enough to frame his brother. I wonder why it was necessary to go to the extra trouble to go all the way upstairs and plant something incriminating in the kid's backpack.
I don't think he was actually framing his nephew as much as trying to give the police a reason to go to his brother's house. Lester probably counted on the blame falling solely on his brother once the police discovered the illegal firearm and the planted evidence.