AFTER MEDICAL RESEARCH IN THE FIELD OF GENETICS REVEALED THE EXISTENCE OF THE XYY CHROMOSOME COMPLEMENT, INDICATING THAT A DISPROPORTIONATE NUMBER OF XYY TRAIT CARRIERS WERE PREDISPOSED TO VIOLENCE, NUMEROUS STUDIES ATTEMPTED TO CONFIRM OR DENY THE THEORY THAT THE Y CHROMOSOME ACTUALLY LEADS TO CRIMINALITY. ALTHOUGH STUDIES DETERMINED THAT MOST XYY CARRIERS WERE ABOVE AVERAGE IN HEIGHT, NO SIGNIFICANT LINK WAS SHOWN BETWEEN THE TRAIT AND AN ACTUAL CAUSE OF CRIME. SEVERAL SCIENTISTS, HOWEVER, BELIEVE THAT THE XYY TRAIT PLAYS SOME PART IN THE FORMATION OF ANTISOCIAL BEHAVIOR. IF SOME LIMITED EFFECT IS MEDICALLY INDICATED, THE CRIMINAL JUSTICE SYSTEM SHOULD TAKE COGNIZANCE OF IT. COURTS MUST DETERMINE WHETHER PUNISHMENT WILL BE INFLICTED UPON A PERSON, WHO BECAUSE OF HIS ABNORMAL GENETIC STRUCTURE, IS READILY INCLINED TO VIOLENCE. A DEFENDANT WHO IS SANE BECAUSE HE UNDERSTANDS RIGHT AND WRONG, MAY STILL BE UNABLE TO FORM THE REQUISITE INTENT TO COMMIT A CRIME. BY ANALOGY TO DRUG ADDICTION AND ALCOHOLISM, THE XYY TRAIT COULD BE CONSIDERED A SICKNESS THEREFORE REQUIRING A JUDGE TO CONSIDER THIS FACTOR IN THE DETERMINATION OF GUILT AND IN SENTENCING. A PERSUASIVE DEFENSE ARGUMENT WOULD BE TO USE THE EXISTENCE OF CHROMOSOME ABNORMALITY TO LESSEN THE PUNISHMENT. TABULAR DATA AND FOOTNOTES ARE PROVIDED. (TWK).