Kripankur Chakraborty, additional district and sessions judge of west Tripura district, held Sushil Choudhury guilty of killing three of his employees May 19, 2013.
"Choudhury is found guilty under sections 120 (B), 109, 302, 113, 111 and 201. Under these sections, the maximum punishment could be either death sentence or life imprisonment," special public prosecutor Dilip Sarkar told reporters after the judgment in a packed court.
He said the judge would announce the quantum of punishment July 17.
Choudhury, 72, editor-cum-owner of Bengali daily Dainik Ganadoot, along with one of his woman employees was arrested weeks after the murder of three employees.
A large number of journalists and others were gathered in the court complex.
Choudhury was the main accused. Niyoti Ghosh, wife of Balaram Ghosh, the slain driver of the newspaper's office vehicle, turned approver in the case and was let off.
Niyoti's husband, manager Ranjit Choudhury, a former BSF employee, and proof reader Sujit Bhattacharjee were murdered in the newspaper's office in the heart of the capital city.