Northern Ireland police say they have arrested Sinn Fein leader Gerry Adams on suspicion of involvement in the Irish Republican Army's 1972 abduction, killing and secret burial of a Belfast widow. Adams confirmed his own arrest Wednesday in a prepared statement and described it as a voluntary, prearranged interview. Police had been expected to question the 65-year-old Adams about the 1972 killing of Jean McConville, whom the IRA executed as an alleged spy. The IRA did not admit the killing until 1998. Adams was implicated in the killing by two IRA veterans who gave taped interviews to researchers for a Boston College research project. The Northern Ireland police took legal steps to acquire the interviews, parts of which have already been published after one IRA interviewee died.