Before revision:  We analyze the bistabilitythresholds of the model, which furthermore possesses robustness of bistability , and provide a model assessment criterion using tools from algebraic geometry .
After revision:  We analyze the bistabilitythresholds of the model, which furthermore possesses robustness of bistability , representing a committed cell death decision, emerges at high concentrations, which may be achieved through receptor pre-association or localization onto membrane lipid rafts. Thus, our model provides a novel theory for these observed biological phenomena within the unified context of bistability. Importantly, as Fas interactions initiate the extrinsic apoptotic pathway, our model also suggests a mechanism by which cells may function as bistable life/death switches independently of any such dynamics in their downstream components .