operant

That operates to produce an effect.

thy most operant poison

I tell you frankly, if Paul Aubry is guilty I hope is convicted and punished; but if one of the others is guilty I hope he—or she—is punished, and if I knew anything operant to that end I certainly would not withhold it.

An operative person or thing.

Any of a class of behaviors that produce consequences by operating (i.e., acting) upon the environment.