In 1972, he presented a scripted report on 'This Week' of an interview he had conducted with IRA chief of staff, Seán Mac Stiofáin. This led to him being called as a prosecution witness in Mac Stiofáin’s trial on a charge of IRA membership. O’Kelly refused to disclose the circumstances under which the statements had been made. Ruled in contempt of court, he was sentenced to three months’ imprisonment and spent two nights in prison. He subsequently became RTÉ’s religious affairs correspondent. He retired from RTÉ in 1986, but continued to present 'Addendum'.