Crowd psychology in South African murder trials

South African courts have recently accepted social psychological phenomena as extenuating factors in murder trials. In one important case, eight railway workers were convicted of murdering four strike breakers during an industrial dispute. The court accepted conformity, obedience, group polarization, deindividuation, bystander apathy, and other well-established psychological phenomena as extenuating factors for four of the eight defendants, but sentenced the others to death. In a second trial, death sentences of five defendants for the "necklace" killing of a young woman were reduced to 20 months imprisonment in the light of similar social psychological evidence. Practical and ethical issues arising from expert psychological testimony are discussed.