How can I make an emergency call in Windows Phone?
If the phone is pin-locked, on the lock screen, when you flick upwards, it is the bottom left button on the dial-pad. The phone does not need to be unlocked to make an emergency call.
If the phone is not pin-locked, to get the emergency services you need to dial the relevant number using the regular dial-pad, which may differ depending on which country you are in (eg. 999 in the UK, 911 in the US).