An ontological investigation into the way of Being for someone in irreversible coma through Martin Heidegger's Dasein-analysis. Ambiguity in the designation 'human being' leads to the conceptual confusion one experiences when encountering someone in irreversible coma, because the designation of 'human being' indicates both 'Homo Sapien' and 'Homo Sapien plus Dasein'. However, considering what he requires for Dasein, Heidegger's Dasein-analysis supports a higher brain function definition of death. Thus on an Heideggerian interpretation, someone in irreversible coma has died as Dasein, remaining in the world as a 'living corpse'.