On 28 January 1612, Ó Duibheannaigh was tried for high treason, found guilty by the majority of a packed jury, and sentenced to die on 1 February (Julian Calendar). He was drawn on a cart from the Castle to the gallows beyond the river; the whole route was crowded with Catholics. Protestant clergymen pestered him with ministrations and urged him to confess he died for treason. "Pray let me be", he answered, "the viceroy's messenger to me here present, could tell that I might have life and revenue for going once to that temple", pointing to a tower opposite. He kissed the gallows before mounting, and then proceeding to exhort the Catholics to constancy, he was thrown off, cut down alive, and quartered.