You are not causing it by the rear touch panel being touched as Unit 13 does not use rear touch, nor does it use the sixaxis to aim as in Uncharted: Golden Abyss. What you are most likely noticing is the auto aim or aim assist type of feature the game employs. It is not an option so it is always on and will try to steer you towards an enemy thats close to the cross hairs. It can screw you up at times by taking shots at a different enemy than you intended; but with some practice it can be really useful. Try to get the aim spot close to an enemys head before pressing the L trigger, once your pretty close quickly press and hold L followed by R then release both. If practiced you will be able to snap off head shots like hotcakes, leading to sick streaks. My personal best for head shot streak is 67!!!