[ethbr1]

In the case of yelling fire, the illegal action would be commiting assault and murder against another person.

When yelling fire without a compelling reason, a reasonable person would anticipate everyone else's standard reaction, and that in the course of that action injury and/or death might occur.

Which is why culpability in the US depends on the speaker's intent. What if I believed I smelled smoke and yelled "Fire" because of that? But was simply wrong?

Unfortunately, intent is impossible to prove definitively, without actually peering into someone else's mind. Thus, can of worms.