Thomas Alva Edison (28) from Tuticorin district in Tamil Nadu killed three of his workers- Dassi, Vijay and Suresh - in February, 2009 for monetary gain of avoiding paying wage arrears due to them, according to the prosecution.
Andrews, another person, also from the neighbouring state, survived the murder attempt.
Awarding the capital punishment, Additional Sessions Judge E M Muhammad Ibrahim found that the "multiple murder" committed by the convict would come within the category of "rarest of rare" case which warranted death penalty as argued by the Additional Public Prosecutor.
"The accused is a threat to the society as he used to create problem wherever he works," the judge said.
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Though Edison was an young man of 24 years as on the date of offence, the court said the three deceased persons were younger than him or in the same age group.
They were roasted alive and they succumbed to burn injuries while another young man, who survived, suffered more than 65 per cent burns, the court said.
His lawyer K P Madhu said an appeal will be filed against the verdict in the Kerala High Court soon.