Firing from third rank

[GreyKatana]

Hi guys.
I have a party which is at the Goblin entrance of the Caves of Chaos. They are in a two column formation in the entrance tunnel, about to be hit by throwed spears from a first group of goblin.
The thief from the third rank wants to throw a dagger. At first I didn't want to allow it but now I'm not so sure. The corridor is roughly ten foot wide, with four guys in front of him. He could squeeze through a take a shot I guess.

Should I allow it, allow it with a penalty, tell him that if he wants to fire he has to move to the front or just plain forbid it? What about if he was on the second rank?

Thanks for your insights.

[greyarea]

I'd say let him throw at a disadvantage and roll for a chance to hit a mate on a miss.

[elf23]

I think I'd rule something like the following:
Missile fire over the heads of shorter folk: no problem. (Front rank halflings, yeah!)
Otherwise penalise it. You could apply a -1 penalty per person in the way? (So -4 in the case you described).