GUILTY PLEAS ENTERED BY DEFENDANTS PRIOR TO TRIAL IN EXCHANGE FOR ASSURANCES OF LENIENCY IN SENTENCING ACCOUNT FOR OVER 90 PERCENT OF ALL CRIMINAL CONVICTIONS IN THE UNITED STATES. THE CONSTITUTIONALITY OF NEGOTIATED PLEAS IS BASED LARGELY ON THE QUESTION OF WHETHER PRESSURES OF THE BARGAINING SITUATION ARE SUCH THAT INNOCENT DEFENDANTS MIGHT BE PERSUADED TO ACCEPT A PROFERRED PLEA BARGAIN AND SUBJECT THEMSELVES TO PUNISHMENT FOR CRIMES THEY DID NOT COMMIT. THE LANDES MODEL, WHICH PREDICTS THAT POLICY MEASURES DESIGNED TO PROVIDE COUNSEL TO DEFENDANTS WITHOUT COST TO THEM WILL INCREASE THE PROPORTION OF TRIALS DEMANDED, IS SUPPORTED BY STATISTICAL EVIDENCE OF A POSITIVE CORRELATION BETWEEN LEGAL EXPENSE SUBSIDIZATION FOR INDIGENT DEFENDANTS AND THE INCIDENCE OF TRIALS IN U.S. DISTRICT COURTS. IN RELATION TO THE LANDES MODEL, THE INITIAL DECISION AS TO WHETHER TO ENTER INTO NEGOTIATIONS AT ALL OR TO INSIST UPON A DETERMINATION OF GUILT OR INNOCENCE AT TRIAL IS DISCUSSED. ASSOCIATED BARGAINING OUTCOMES PREFERRED BY PROSECUTORS AND DEFENDANTS OVER THE PROSPECT OF A FULL TRIAL ARE EXAMINED, WITH THE SET OF BARGAINING OUTCOMES SEEN BY BOTH PARTIES AS PREFERRED ALTERNATIVES TO TRIAL GIVEN THE EXISTENCE OF A CONTRACT ZONE. A DYNAMIC MODEL OF BARGAINING BEHAVIOR IS PRESENTED THAT PORTRAYS THE ACTUAL PROGRESS OF PLEA NEGOTIATION ITSELF AND SPECIFIES THE EVENTUAL OUTCOME OF NEGOTIATION IN CASES WHERE THERE IS A NONEMPTY CONTRACT ZONE. THE MODEL REPRESENTS A BEHAVIORAL APPROACH AND INVOLVES DECISION, EXPECTATION, AND ADJUSTMENT. IT IS SUGGESTED THAT THE PLEA NEGOTIATION PROCESS MAY ENCOURAGE RESULTS FEARED BY THE U.S. SUPREME COURT, SINCE THE INTRODUCTION OF TIME-RELATED COSTS AND THEIR ATTENDANT INCENTIVES AS SIGNIFICANT FACTORS IN DECISIONS OF DEFENDANTS TO PLEAD GUILTY ADDS A DIMENSION TO DEFENDANT BEHAVIOR THAT IS ENTIRELY UNRELATED TO GUILT OR INNOCENCE. ENDEMIC EPISTEMOLOGICAL PROBLEMS ARISE AT THE INTERFACE OF LAW AND SOCIAL SCIENCE AND SERVE TO DELIMIT THE RELEVANCE OF FORMAL ECONOMIC ANALYSIS IN MANY ADJUDICATIVE SETTINGS. REFERENCES ARE INCLUDED, ALONG WITH MATHEMATICAL EQUATIONS DEVELOPED IN THE MODELING PROCESS. (DEP)