WASHINGTON -- A prominent group of polling researchers has accused the lead author of a 2006 study suggesting massive civilian deaths in Iraq of violating the polling profession's codes and ethics. The Executive Council of the American Association for Public Opinion Research said Dr. Gilbert Burnham, a Johns Hopkins University professor, had repeatedly refused to cooperate with an eight-month investigation into his research on the Iraqi death toll that made headlines in October 2006 when it was published by The Lancet, a British medical journal.