Sinn Fein President Gerry Adams was arrested Wednesday as part of an investigation into one of Northern Ireland's most controversial killings. Neil Hall/Reuters /Landov hide caption

itoggle caption Neil Hall/Reuters /Landov

Queen Elizabeth II shook hands with Deputy First Minister of Northern Ireland Martin McGuinness today in Belfast. McGuinness is a former senior member of the IRA. Paul Faith/WPA Pool/Getty Images hide caption

itoggle caption Paul Faith/WPA Pool/Getty Images