My wife once put down some poison and it worked, a mouse died on an underfloor central heating pipe. That weekend the bathroom was unusable as we pulled up the floor covering and all floor boards in an attempt to find the cause of the horrible dead mouse smell that filled the room. Never again has poison been used - spring traps are the way to go.
One other point: you can always put the UNpoisened, spring trap caught, body out somewhere for other animals. If you have a suitable area there are plenty of scavengers out there that would be pleased of a meal and then at least the mouse will not have died in vain.
ChrisG