MY BATTERY IS DEAD AND I CAN NOT OPEN THE TRUNK.

Find the post forward of the driver side fuse box in the engine compartment. This is where a bunch of wires come together. This is a positive terminal. Attach red jumper here and black to any bare metal bracket in the engine.

Just use the metal key .Pull it out of the plastic ,electronic key and put it in the key slot which is next to the trunk handle and turn it .The trunk should open even if the battery is dead.No need to go under hood.Well it works on my 2003 amg 55