A CONFLICT EXISTS BETWEEN THE TWO DIFFERENT EPISTEMOLOGIES OF LEGAL JUSTICE AND SOCIAL SCIENCE, ALTHOUGH BOTH DEAL WITH THE SAME SUBJECTS. WHILE THE COURT HAS BEGUN TO HEAR ARGUMENT BASED ON RESEARCH DATA, IT REMAINS BIASED TOWARD THE LEGAL PERSPECTIVE. IN WILLIAMS VERSUS FLORIDA, THE COURT HELD THAT JURY SIZE IN NONFEDERAL CASES WAS NOT CONSTITUTIONALLY GUARANTEED AND CITED RESEARCH SUGGESTING THAT A JURY OF SIX IS AS RATIONAL, RESPONSIBLE, AND RELIABLE AS ONE OF TWELVE MEMBERS. UNFORTUNATELY, IN THIS CASE THE COURT BASED ITS FINDINGS ON THREE ARCHIVAL ANALYSES, WHICH AS A RESULT OF THEIR RETROSPECTIVE NATURE LACKED ANY FORM OF EMPIRICAL CONTROL. THE FOURTH STUDY ON WHICH THIS DECISION WAS BASED WAS A SIMULATION WHICH CONTAINED SO MANY METHODOLOGICAL FAULTS AS TO RENDER IT INVALID. FURTHER, JURY SIMULATIONS GENERALLY CONTAIN SERIOUS METHODOLOGICAL PROBLEMS, RARELY ANALYZE THE GROUP PROCESSES ACTIVE IN JURY DECISIONMAKING, AND CANNOT POSSIBLY CONTROL FOR ALL THE VARIABLES OPERATING IN EITHER A SIMULATION OR AN ACTUAL TRIAL. FINALLY, SAMPLE SIZES IN THE STUDIES CITED BY THE COURT WERE QUITE SMALL. LEMPERT'S (1975) ARTICLE ON JURY SIZE RESEARCH IS REVIEWED. ON THE BASIS OF RESEARCH LEMPERT SUGGESTS THAT THE QUALITY OF VERDICTS BY 12-MEMBER JURY WILL BE OF HIGHER QUALITY THAN THAT OF 6-MEMBER JURIES. IN JOHNSON VERSUS LOUISIANA AND IN APODACA VERSUS OREGON, THE COURT HELD THAT A 9 OUT OF 12 VOTE BY A CRIMINAL TRIAL JURY IS SUFFICIENT TO RETURN EITHER A GUILTY OR NOT GUILTY VERDICT AND DOES NOT DEPRIVE THE DEFENDANT OF DUE PROCESS OR EQUAL PROTECTION. GROUP DYNAMICS AND JURY DECISIONMAKING LITERATURE, HOWEVER, SUGGEST THAT JURIES ARE CONVICTION PRONE TO BEGIN WITH AND THAT SWITCHING FROM A UNANIMOUS VOTE TO A MAJORITY VOTE MAKES THE LIKELIHOOD OF CONVICTION AS MUCH AS THREEFOLD. IT IS SUGGESTED THAT RELAXATION OF THE UNANIMOUS VOTE STANDARD INCREASES THE CHANCES FOR A MISCARRIAGE OF JUSTICE, PARTICULARLY IN WEAK CASES. IN TWO OF THREE JUDGEMENTS PERTAINING TO PREJUDICIAL EFFECTS OF INADMISSABLE TESTIMONY, THE COURT RULED THAT CAUTIONARY INSTRUCTIONS BY THE JUDGE TO THE JURY WERE SUFFICIENT TO ERASE THE EFFECTS OF INADMISSABLE TESTIMONY. IN GENERAL, RESEARCH CONTRADICTS THIS AND PROVIDES SUPPORT FOR THE OPPOSITE CONCLUSION PUT FORTH IN THE 1968 BRUTON DECISION. THE SUPREME COURT DECISIONS ON JURY SELECTION PROCEDURES, WHICH HELD THAT DUE PROCESS RIGHTS ARE VIOLATED BY EXCLUDING JURORS PREJUDICED AGAINST CAPITAL PUNISHMENT, IS SUPPORTED BY RESEARCH INDICATING THAT DEATH PENALTY PROPONENTS ARE MORE PUNITIVE AND HIGHLY CONVICTION PRONE. TEXT BEARING ON THIS QUESTION AS PRESENTED IN NORTH CAROLINA VERSUS JOAN LITTLE IS INCLUDED AS AN EXAMPLE OF COOPERATION BETWEEN SOCIAL SCIENCE AND THE COURT. NOTES AND REFERENCES ARE ALSO PROVIDED. (JAP)