How can I kill my iPhone when my location service is turned off?
If the iPhone has no power, there is nothing you can do as it cannot be found.
Find My Iphone only works with an iPhone turned on.

You could check regularly if they power on the iPhone, you can put it on the loud sound or clean it remotely. Offline/Without power there is nothing you can do.

If your iPhone was running iOS7 and iCloud is enabled the thieves cannot restore the iPhone, so they cannot sell it.