>If the officer demands that you turn on your device but the battery is dead then it mean that you are unable to comply. Ah ha! A clever loophole that no one has ever thought of before.

Yeah....about that:

http://www.etihad.com/en-us/before-you-fly/us-preclearance/

All guests travelling to the US, UK or Canada from Abu Dhabi International Airport are required to turn on all electronic devices in their possession prior to boarding. Guests must ensure that all electronic devices in their hand luggage or on their person, including mobile phones, tablets and laptops, are charged to minimize any potential disruption to their journey.

Abu Dhabi Airport does not have a facility to store devices, which cannot be powered up and Etihad Airways cannot take responsibility for devices which are left behind.

This requirement is part of enhanced security measures by the authorities of these countries. Failure to do so may result in not being allowed to take the device(s) onto the aircraft or being denied access to fly.