It's possible. I would guess this is a bug, backstab just needs to be added to the list of disallowed commands in jail.
Quote:
[HP:100%] [ME:100%] [PE:100%]
>
Edman stops resting, and clambers to his feet.
[HP:100%] [ME:100%] [PE:100%]
>
You yell 'Guards! Edman is trying to murder me!'
Suddenly Edman stabs you in the back!
That really did HURT!
[HP: 46%] [ME:100%] [PE:100%]
>
You miss Edman.
Edman stabs your chest HARD, piercing through your ribs!
You are coughing up BLOOD!
Edman stabs your head, carving a bleeding hole in it!
Edman raises his weapon and thrusts it deep into your chest!
You are coughing up BLOOD!
Overall, Edman is in excellent condition.
[HP: 11%] [ME:100%] [PE:100%]
>
Your punch at Edman's right arm is deflected by a set of mithril sleeves.
Your chest is ripped apart from massive damage!
Everything goes dark!
You have been KILLED!!
[HP: 0%] [ME:100%] [PE:100%]
>
Edman grunts.
[HP: 0%] [ME:100%] [PE:100%]
>
[HP: 0%] [ME:100%] [PE:100%]
> l
Grim Dungeon
The light pouring in from a tiny, iron-grated window is insufficient to
pierce much of the damp darkness of this dungeon. Unfortunately, no benches
nor beds can be seen, nor even a pile of straw, and the hard, stone floor
here is most unforgiving.
Obvious exits: u(closed)
The corpse of Pyras is lying here.
The severed foot of Pyras is here.
( 6) A leather waterskin lies here.
Edman is here.