ALL STUDIES THAT EXPLORE STATISTICALLY THE POSSIBILITY OF A DETERRENT EFFECT OF CAPITAL PUNISHMENT BEYOND THAT OF LIFE IMPRISONMENT ARE ATTEMPTS TO SIMULATE THE CONDITIONS OF AN IMPOSSIBLE CONTROLLED EXPERIMENT. AN ANALYSIS OF THESE ATTEMPTS CONCLUDES THAT THE EVIDENCE, RATHER THAN BEING INCONCLUSIVE AS SOME CLAIM, IS DECIDEDLY AGAINST THE EXISTENCE OF A SPECIAL DETERRENT EFFECT FOR CAPITAL PUNISHMENT. IF THERE IS SUCH AN EFFECT IT MUST BE A MINUTE ONE, BECAUSE REGARDLESS OF HOW SENSITIVE THE MEASURE OR HOW SOPHISTICATED THE TECHNIQUE OF ANALYSIS, RESEARCHERS HAVE FAILED TO DETECT IT. THE QUESTION APPEARS TO BE WHETHER AN EFFECT SO SMALL AS TO BE VIRTUALLY UNDETECTABLE CAN POSSIBLY JUSTIFY THE CONSIDERABLE MORAL COSTS OF THE DEATH PENALTY--THE INHUMANITY OF THE ACT, THE EVER-PRESENT DANGER OF ERROR, THE ULTIMATE IMPOSSIBILITY OF MAKING A FAIR DECISION REGARDING WHO SHOULD DIE AND WHO SHOULD LIVE. RELUCTANCE TO ABANDON CAPITAL PUNISHMENT STEMS NOT FROM A BELIEF IN ITS DETERRENT EFFECT, BUT FROM MORAL SENTIMENTS AND A LONGSTANDING BELIEF IN RETRIBUTIVE JUSTICE. A REVIEW OF THE CIRCUMSTANCES SURROUNDING ABOLITION OF THE DEATH PENALTY IN OTHER COUNTRIES SHOWS THAT ABOLITION IS A MATTER OF CULTURAL SENTIMENT RATHER THAN CONSIDERATIONS OF DETERRENT EFFECTIVENESS. IT MAY BE THAT THE IMPORTANCE OF THE DETERRENCE ISSUE IS OVERESTIMATED. SUPPORTING DATA ARE INCLUDED. (LKM)