SRD:Detect Law

You can sense the presence of law. The amount of information revealed depends on how long you study a particular area or subject.

1st Round: Presence or absence of law.

2nd Round: Number of lawful auras (creatures, objects, or spells) in the area and the power of the most potent lawful aura present.

If you are of chaotic alignment, and the strongest lawful aura’s power is overwhelming (see below), and the HD or level of the aura’s source is at least twice your character level, you are stunned for 1 round and the spell ends.

3rd Round: The power and location of each aura. If an aura is outside your line of sight, then you discern its direction but not its exact location.

Aura Power: An lawful aura’s power depends on the type of lawful creature or object that you’re detecting and its HD, caster level, or (in the case of a cleric) class level; see the accompanying table. If an aura falls into more than one strength category, the spell indicates the stronger of the two.

Lingering Aura: A lawful aura lingers after its original source dissipates (in the case of a spell) or is destroyed (in the case of a creature or magic item). If detect law is cast and directed at such a location, the spell indicates an aura strength of dim (even weaker than a faint aura). How long the aura lingers at this dim level depends on its original power:

Animals, traps, poisons, and other potential perils are not lawful, and as such this spell does not detect them.

Each round, you can turn to detect lawful in a new area. The spell can penetrate barriers, but 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt blocks it.