Mr. Trninić was born in 1956, in the settlement of Ramići, in the municipality of Ključ.
He graduated from the faculty of mechanical engineering in Banja Luka. He has worked as a professor in the Secondary Education Centre in Ključ, and has held managing positions in commercial sector – as a Production Manager at the Furniture Factory “Previja” in Ključ, Technical Manager of electromechanical maintenance at the Mine of lead and zinc “Sase” Srebrenica, and then the Technical Director at the Factory for processing lightweight, non-ferrous and precious metals “11. mart”' in Srebrenica.
From the year 2000 to 2004, he has been the General Manager of the Factory for Galvanizing Ltd, Srebrenica, which has been prized as one of the most successful companies in the Republic of Srpska on several occasions.
He is a holder of a series of awards from the Chamber of Commerce of the Republic of Srpska, for his achievements in commercial sector.
He is the Chairperson of the Regional Chamber of Commerce Bijeljina Council and the Managing Board Member of the Chamber of Commerce of the Republic of Srpska in the field of metal industry.
Until 2011, he has been a permanent court-expert in the field of mechanical engineering.
He has been a councillor in the Municipal Assembly of Bratunac in the period from 1997 to 2010, and a delegate at the National Assembly of the Republic of Srpska between 2010 and 2014.
He has participated in the defensive-homeland war of the Republic of Srpska from 1992 to 1995.
Since 2014, he performs the function of the Minister of transport and communications at the Government of the Republic of Srpska, and in 2017, he has been awarded as "The Best Minister in the Republic of Srpska" by the Directorate of European Agency for Selection and Promotion of Best Managers and Best Companies.
He lives in the town of Bratunac, he is married, a father of two sons and a grandfather of two grandchildren.
By nationality he is a Serb.