No, I was suggesting that he pretend that the controller he swapped was his brothers here is a better clearer scenerio.
His brother has his controller, and it's in his room. He has his brothers controller.
He goes into his brothers room, and swaps his brothers controller for his own controller.
He sneaks out of his brothers room, and goes into his own room, and marks the controller.
He goes to his mom, and says "Mom, I marked my controller with a X. So if he has a controller with a X, on it. It's mine."
He places the controller in his room, and leaves.
His brother goes into his room, and takes the controller marked with a X, and leaves the other one.
He goes into his room, notices his controllers been swapped, and tell his mom.
His mom goes into his brothers room, and takes the controller, and looks for the X.
She finds the X, and believes that his brother took his controller.
His brother is punished.
^Win.
Or...
Gordinio said:
OP: Sneak in and add the marking, then tell your mother that he has your controller.
^This.