Having trouble with some of his uncle's tenants, Chadwick, in May 1827, had permission to erect a police barracks at Rathcannon, in order to curb and monitor the activities of secret societies operating in the area.

Grace was tried at Clonmel Assize in July 1827 and, convicted on 17 August on the evidence of Philip Mara, was hanged at the scene of the murder in Rathcannon on 20 August 1827; he admitted his guilt on the gallows and urged his brothers, and others present, to desist from unlawful practises.

Another brother of Philip Mara fled for safety to Borrisokane, where at attempt was made to shoot him while he was at Mass.

In March–April 1828, Patrick Lacy and John Walsh were tried for the murder of Daniel Mara and convicted, the main witnesses for the prosecution being their accomplices, Thomas Fitzgerald (who was arrested while participating in an armed robbery near Killenaule and, while in jail in Clonmel, turned informer to save himself) and Edmond Ryan of Ballymoreen.

William Grace, Thomas Keogh, Michael Treacy, Thomas Maher, Michael Luby and James Daniel who had changed their pleas to guilty were also sentenced to death but an express messenger arrived from the Marquis of Anglesea, the Lord Lieutenant, with an order to commuting their execution to transportation.