Senior Magistrate Nanette Forde-John handed down the verdict Wednesday in Scarborough.
Dumas was charged with hitting a Trinidadian man, Roger Simon, also known as “Abdul Jabar”, in his face with a licensed firearm, knocking out several of Simon’s teeth.
The court found Dumas guilty of assault occasioning actual bodily harm, and common assault. Dumas is to reappear in court for sentencing on May 2.
Dumas is a former member of Parliament for Tobago East and served in the Manning Cabinet as Labour Minister.