On January 11, 1839, de Lorimier and three of his comrades (two of whom managed to escape before being executed; the other was Chevrier Bénard) appeared before the British Council of War.
Refused his request for a trial in a civilian court, de Lorimier apparently effectively defended himself and challenged the crown's evidence.
However, Jean-Baptiste-Henri Brien, one of his co-accused and terrified of the scaffold, signed a confession incriminating de Lorimier and others and the British authorities, having failed to seize the main leaders of the rebellion, arguably pursued his death to make an example.
On January 21 de Lorimier and his companions were found guilty of high treason and sentenced to be hanged which took place on February 15, 1839, together with Charles Hindelang, Amable Daunais, François Nicolas and Pierre-Rémi Narbonne.
The day before, de Lorimier wrote his political testament: I die without remorse; in the insurrection I only desired the well-being and independence [from Britain] of my country.