death by cat would be extreme cruelty to the mice ....
Well, the mice will learn very fast, after 'sacrificing' one or
two of their comrades, that it's best for them to up and go and
choose somewhere safer to thrive in. 
There... problem solved! No need to freeze, smash, drug, snap
the spine, what-not-shit. Clean, simple, easy. (And the
cat does the dirty job, not you!)
