AT ISSUE ARE SITUATIONS IN WHICH ONE ATTORNEY REPRESENTS BOTH TARGET AND NONTARGET WITNESSES IN A GRAND JURY INVESTIGATION OF WHITE COLLAR CRIME, ORGANIZED CRIME, OR OFFICIAL CORRUPTION, THEREBY FACILITATING A 'STONEWALL' DEFENSE ON THE PART OF TARGET WITNESSES. THE NATURE OF THE OBSTACLE POSED BY COMMON REPRESENTATION TO THE SUCCESS OF A GRAND JURY INVESTIGATION IS DESCRIBED. ALSO DETAILED ARE THE VARIETY OF JUDICIAL RESPONSES TO THIS OBSTACLE AND THE SPECIFIC ETHICAL AND DISQUALIFICATION ISSUES RAISED BY THESE RESPONSES. AN ANALYSIS OF ETHICAL STANDARDS RELATING TO ADEQUACY OF REPRESENTATION CONCLUDES THAT SUCH STANDARDS ARE SATISFIED ONCE WITNESSES HAVE BEEN INFORMED OF THE POTENTIAL DANGERS OF COMMON REPRESENTATION AND STILL GIVE THEIR CONSENT. AN ANALYSIS OF ETHICAL STANDARDS RELATING TO THE ATTORNEY'S OBLIGATION NOT TO IMPEDE THE ADMINISTRATION OF JUSTICE CONCLUDES THAT, WITH CERTAIN EXCEPTIONS, THE COMPONENTS OF A STONEWALL DEFENSE ARE ETHICALLY PERMISSIBLE. IN VIEW OF THESE CONCLUSIONS, STANDARDS FOR DISQUALIFYING ATTORNEYS IN MULTIPLE REPRESENTATION CASES ARE SUGGESTED. IN DECIDING WHETHER A WITNESS' PURPORTED CONSENT TO COMMON REPRESENTATION IS BOTH INFORMED AND VOLUNTARY, COURTS ARE ADVISED FIRST TO CONSIDER THE LIKELIHOOD THAT ONE WITNESS CAN INCRIMINATE ANOTHER, AND THEN TO CONSIDER CIRCUMSTANCES, SUCH AS THE COERCION INHERENT IN EMPLOYER-EMPLOYEE RELATIONS, THAT RAISE SERIOUS DOUBTS ABOUT VOLUNTARINESS. DISQUALIFICATION MIGHT ALSO BE WARRANTED TO PREVENT CLEARLY UNETHICAL CONDUCT, SUCH AS FACILITATION OR KNOWING USE OF PERJURY, BUT ONLY AFTER A NONTARGET WITNESS HAS BEEN IMMUNIZED AND ORDERED TO TESTIFY. ONLY THEN WOULD THE IMPORTANCE OF PRESERVING THE INTEGRITY OF A GRAND JURY INVESTIGATION OUTWEIGH THE INTERESTS OF WITNESSES WHO CHOOSE TO BE REPRESENTED BY A COMMON ATTORNEY. FOOTNOTES ARE PROVIDED. (AUTHOR ABSTRACT MODIFIED)