The Supreme Court will begin an appeal hearing on Tuesday into the death sentence handed down to the lone surviving gunman from the 2008 Mumbai attacks.
Ajmal Kasab, one of 10 gunmen who laid siege to Mumbai in attacks which lasted nearly three days and killed 166 people, has appealed for his sentence to be overturned after he was convicted in May 2010.
The 24-year-old Pakistani was found guilty of a series of crimes, including waging war against India, murder and terror acts.
The November 2008 attacks saw 10 heavily-armed Islamist gunmen storm targets including luxury hotels, a Jewish centre and a train station.
Two Supreme Court judges in New Delhi will hear the appeal, which is expected to last several weeks after opening with a statement from Kasab's court-appointed counsel Raju Ramachandran.
"It is a call of duty," Ramachandran told AFP by telephone, declining to talk further about the case.
India blames the Pakistan-based Lashkar-e-Taiba (LeT) militant outfit for training, equipping and financing the attack with support from "elements" in the Pakistan military.
Kasab's death sentence was confirmed by a state high court in Mumbai last year. If he loses his Supreme Court appeal, he will be able to appeal for clemency from the President.
Ujjwal Nikam, who prosecuted the case in Mumbai on behalf of the Maharashtra state, is seeking to push through the death sentence.
"This is the rarest of rare cases," Nikam told AFP ahead of the hearing.
"He should not be entitled to any mercy."
At the trial, the prosecution produced fingerprint, DNA, eye-witness and television evidence showing him opening fire and throwing grenades at Mumbai's main railway station in the bloodiest episode of the attacks.
Kasab -- who is in jail in Mumbai -- initially pleaded not guilty but later made a confession, admitting to being one of the gunmen sent by the banned LeT militant group.
He then reverted back to his initial denial and said he was framed by the police.
Pakistan has indicted seven alleged perpetrators behind the attacks but they have not been brought to trial, triggering Indian accusations that the process is a sham.
Pakistani investigators and lawyers will visit India next month to gather more evidence ahead of any trial in Islamabad.
Most death sentences in India are commuted to life imprisonment, and convicts can sit on death row for years awaiting a final decision.