breath weapon when helpless

[TheDanimal]

If I use icy prison to trap a half red dragon. It fails its save, can it use its breath weapon since its a supernatural ability which is -mental- according my dm to free itself.

[PrinceDogWaterIII]

Helpless:

A helpless character is paralyzed, held, bound, sleeping, unconscious, or otherwise completely at an opponent's mercy. A helpless target is treated as having a Dexterity of 0 (–5 modifier). Melee attacks against a helpless target get a +4 bonus (equivalent to attacking a prone target). Ranged attacks get no special bonus against helpless targets. Rogues can sneak attack helpless targets.

As a full-round action, an enemy can use a melee weapon to deliver a coup de grace to a helpless foe. An enemy can also use a bow or crossbow, provided he is adjacent to the target. The attacker automatically hits and scores a critical hit. (A rogue also gets his sneak attack damage bonus against a helpless foe when delivering a coup de grace.) If the defender survives, he must make a Fortitude save (DC 10 + damage dealt) or die. Delivering a coup de grace provokes attacks of opportunity.

Creatures that are immune to critical hits do not take critical damage, nor do they need to make Fortitude saves to avoid being killed by a coup de grace.

Where does it say a helpless character cannot use a standard action(or swift)? The spell even states even if the creature fails it's save it can still breathe.

Icy Prison:

You trap the target in solid ice 1 inch thick per caster level. If the creature fails its save, it is helpless, but can still breathe (the ice blocks line of effect to the target). If the target makes its save, it gains the entangled condition but can otherwise act normally. Whether or not the target saves, it takes 1 point of cold damage per caster level each round it is helpless or entangled in the ice. The ice has hardness 0 and 3 hit points per inch of thickness; if broken, the creature is freed. A creature can break the ice as a full-round action with a successful Strength check (DC 15 + your caster level).

Not anywhere in the rules but if you can breathe I'm pretty sure you can use your breath weapon.

[blahpers]

A character with 0 Dex cannot move and is effectively immobile. Most standard actions require significant movement. But, in this case, your GM will have to decide. Not all helpless conditions are created equal.

[Korthis]

If its helpless and you don't need it alive coup de gras

[Zhayne]

Since this action involves the body and not the mind, I would not rule it to be a mental action.

[Benrislove]

related, Dimensional Steps, Shift, or a demon using greater teleport?

SLAs don't have verbal, somatic, or material components (like supernaturals).

I would assuming casting dimension door is a "no" because even verbal components wouldn't work while trapped helplessly.

purely mental actions though? Shift and Dimensional Steps both are void of any components.