Uday Chand Kumar, owner of the shelter home in Gurap in Hooghly district, and his friend Shyamal Ghosh were convicted for rape and murder after the body of a 31-year-old woman was exhumed from inside the home in July 2012.
While the state police Criminal Investigation Department (CID) filed a chargesheet in October 2012, the Calcutta High Court later directed the Central Bureau of Investigation (CBI) to take over investigation, expressing dissatisfaction with the CID probe.
The CBI investigation later revealed that at least three more inmates were similarly tortured and murdered.
Convicting them of rape and murder, the court of Hooghly Sessions Judge Arup Basu sentenced Ghosh and Kumar to life imprisonment.
"We sought death sentence for the accused contending that the case fell in the category of rarest of rare, but the court, considering their age perhaps, sentenced them to life," the public prosecutor said.
The state will appeal in the high court seeking death penalty, he added.