A series of isatin sulfonamide analogs having a Michael acceptor were prepared and their potencies for inhibiting caspase-1, -3, -6, -7, and -8 were evaluated. These compounds have nanomolar potency for inhibiting the executioner caspases, caspase-3 and caspase-7, and have a low potency for inhibiting caspase-1, caspase-6, and caspase-8. The inhibition mechanism was investigated through NMR studies of the reaction between 11d and benzylmercaptan as a model for Cys-285 in the active site of caspase-3.