The incident had happened on August 14, 2006 when Mandar had gone out with his friends who kidnapped him and demanded ransom of Rs 50 lakh from his father.
They allegedly killed him when their plan turned failed.
Mandar's body was found on August 16 at Ponda and police arrested the five boys, who were minors at the time of the crime, on the same day.
One of the accused later turned an approver.
According to the prosecution, Madar was injected with vodka shots twice before he was killed by the accused.