Born in St. James Parish, Louisiana to a family of French Acadian origin,[1][2][3] Poché was educated at the public schools of Louisiana until he reached the age of sixteen, and was then sent to St. Joseph's College at Bardstown, Kentucky, and after leaving that school in 1855 he remained for a time in Bardstown, reading law in the office of former Governor Charles A.

[3][1] After having been admitted to the bar of Kentucky, he went to Louisiana and continued his legal studies in the office of Judge Roman of Thibidiaux, in the Parish of Lafourche, and was admitted to the bar of Louisiana in 1859.

[1] Poché served in the Confederate Army during the American Civil War, entering the service as Captain of Infantry in June, 1862.

[1][3] In 1878, Poché was one of the founders and charter members of the American Bar Association, and was a vice-president of that organization for eight years.

[1] In 1880, Poché was appointed the senior associate justice of the newly reconstituted Louisiana Supreme Court for a term of ten years.