Former Irish Republican Army members and Sinn Fein party colleagues say Northern Ireland police are casting a wide net in efforts to prove that party leader Gerry Adams once commanded the outlawed IRA and ordered the 1972 killing of a Belfast mother of 10.

Details of evidence being sought emerged Saturday as detectives spent a fourth day questioning Adams about the IRA's abduction, killing and secret burial of Jean McConville. The IRA admitted responsibility in 1999. Her remains were found in the Republic of Ireland in 2003.

IRA veteran Peter Rogers says a detective approached him to testify against Adams but he refused. Rogers says Adams told him in 1980 to smuggle unstable liquid explosives to England.

Sinn Fein officials say detectives are questioning Adams about much of his writings.