Spoiler : New theory :
This makes absolutely zero psychological sense, but at least it's red-bait.
The true culprit was Edgeworth, who was blackmailing Franziska and Larry in order to pursue his dream of creating an awesome locked room mystery. He threatened to kill everyone they cared about if they didn't follow orders. Maybe he had an assassin waiting on orders or something.
First, he gave Franziska a key and a piece of tape. Then he shot Larry with one gun and Franziska with the other in a way that would lead to death by blood loss. They were under orders to enter the courtroom and stand in position holding the guns. Franziska was to lock the door behind herself and tape the key to her forehead.
The gamble was this: if they died of their wounds at the right time, he'd have created a locked room, but if they survived their wounds, he would be convicted of the murders. Knowing this, the two followed orders in the hope of surviving their wounds.
Note that the Santa costume that Larry was wearing could possibly hide a wound...
The true culprit was Edgeworth, who was blackmailing Franziska and Larry in order to pursue his dream of creating an awesome locked room mystery. He threatened to kill everyone they cared about if they didn't follow orders. Maybe he had an assassin waiting on orders or something.
First, he gave Franziska a key and a piece of tape. Then he shot Larry with one gun and Franziska with the other in a way that would lead to death by blood loss. They were under orders to enter the courtroom and stand in position holding the guns. Franziska was to lock the door behind herself and tape the key to her forehead.
The gamble was this: if they died of their wounds at the right time, he'd have created a locked room, but if they survived their wounds, he would be convicted of the murders. Knowing this, the two followed orders in the hope of surviving their wounds.
Note that the Santa costume that Larry was wearing could possibly hide a wound...