While the conviction was upheld, the apex court observed that it was not the rarest of the rare cases to uphold the death sentence awarded to Singh by the Delhi High Court.
"The conviction is maintained," the court said.
Bench comprising Justices HS Bedi and CK Prasad, however, added, "To our mind, certain things are in favour of appellant (Singh). We are converting the punishment of death sentence into the life imprisonment."
The CBI had sought the apex court to uphold the death sentence given to Singh citing that the HC had sentenced him based on solid evidence.
The convict, who is a son of former senior IPS officer, had challenged his conviction and death sentence handed by the Delhi HC in Oct 2006.
The High Court had set aside the Singh's Dec 1999 acquittal by the trial court in the case.
Singh, a law student in the Delhi University, had raped and murdered Priyadarshini, a third-year law student, in Jan 1996.