You are assuming a dead mans switch that is not set up (whether technical or depending on people) to get triggered if he is taken into US custody.
Given his previous statement that he "can't be" tortured to give up the information he has, I am assuming he does not himself have direct control of the dead mans switch, but have left information to other parties on when to release, so it might be entirely out of both his hands and the US governments hands whether or not their actions will trigger "the switch".
Given his previous statement that he "can't be" tortured to give up the information he has, I am assuming he does not himself have direct control of the dead mans switch, but have left information to other parties on when to release, so it might be entirely out of both his hands and the US governments hands whether or not their actions will trigger "the switch".