Additional Sessions Judge Deepak Aggarwal sentenced Kuldeep Manga, Gobind Sharma, Vikram Bantee and Naveen to life term for murdering Rakesh alias Bobby.
However, five other accused were acquitted due to insufficient evidence.
Rakesh was shot dead on March 3, 2010, after coming out of court in connection with a case against him.
During the course of the trial, Rakesh's sister Rutu, who was a witness in the case, was shot dead.
According to prosecution, Rakesh was a gangster involved in several serious offences.
They were arrested later.
Police had registered a case of murder and conspiracy against nine persons in this regard.