Aarushi was found with her throat slit in her bed, just days before she turned 14. At first, Hemraj, who was missing, was the main suspect, but the next day, his body was found on the roof of the apartment building where the Talwars lived.
Rajesh Talwar was arrested seven days after the murder and spent two months in jail before getting bail. Both Rajesh and his wife, Nupur, have been in jail since November 2013.
The case became a sensational story dividing public opinion on who killed Aarushi; a book and a film have been made on the double murder.
The CBI had asked for the death penalty when the Talwars were convicted by a local court in Ghaziabad four years ago.
Early in the investigation, the Noida police alleged Rajesh Talwar had murdered Aarushi and Hemraj in a rage after finding them in a compromising situation. But they offered no forensic or material evidence to substantiate this claim.
The Talwars deny the murder and blame sensational media coverage for demonising them and damaging their defence.
The judge who found them guilty four years ago said they had also destroyed evidence.
The initial police investigation was widely criticised, prompting the CBI to take over the case. It based its prosecution largely on circumstantial evidence, but said it was enough to prove that the couple had committed the crime.
In December 2010, the CBI told the court that it had no evidence in the case but suspected Rajesh Talwar of the double murder. The court said that the case could not be closed.
The CBI has said that there's no evidence of the Talwars' home being broken into, which suggests the double murder was an inside job. It has also argued the "last-seen theory" -- which holds that the victims were last seen with the Talwars on the night that the murders were committed.