ˌɛni ɹᵻlˈiːs ʌv ɹˌeɪdɪoʊæktˈɪvᵻɾi, dɪtˈɛktᵻd baɪ ɐ dʒˈaɪɡɚ kˈaʊntɚ, wʊd tɹˈɪɡɚɹ ɐ dɪvˈaɪs ðæt wʊd kˈɔːz ɐ hˈæmɚ tə ʃˈæɾɚɹ ɐ ɡlˈæs vˈaɪəl kəntˈeɪnɪŋ pɹˈʌsɪk ˈæsɪd, hˈɛns kˈɪlɪŋ ðə kˈæt.
Any release of radioactivity, detected by a Geiger counter, would trigger a device that would cause a hammer to shatter a glass vial containing prussic acid, hence killing the cat.