The court said the prosecution had succeeded in proving the charges against them, including murder, unlawful assembling and destruction of evidence.
Judge R Raghu, who pronounced the verdict, also observed that nine convicts had direct links to the murder, which occurred in 2009 while four others were sentenced to three years imprisonment. The 14th accused was acquitted.
The special court also slapped a fine of Rs 50,000 on the first convict Jayachandran and Rs 55,000 each on the next seven convicts.
The Kerala High Court had ordered a CBI inquiry into the case next year on a petition filed by Paul's father and Muthoot business group Chairman M G George.