[1] He was the law partner to Rufus Easton in St. Louis and St. Charles and remained in this position until he was killed in a duel.
In August 1817 Lucas and Benton as attorneys were opposite sides of a court case and accused each other of lying.
Benton replied that he owned slaves and paid taxes on them and could vote and then called Lucas according to one version an "insolent puppy."
Lucas then challenged Benton on August 11 to a duel with a note, "I am informed you applied to me on the day of the election the epithet of 'Puppy.'
On September 23 Benton challenged Lucas to a rematch, saying "When I released you from your engagement to return to the island, I yielded to a feeling of generosity in my own bosom, and to a sentiment of deference to the judgment of others.
The object of this is to bring these calumnies to an end, and to give you an opportunity of justifying the great expectation which has been excited.