Here are the 10 latest developments in the story:
The President is likely, said sources, to reject tonight a new mercy plea filed by Memon, which means he will be executed in Nagpur early tomorrow morning.
The Home Ministry has reviewed the new mercy petition as required and Mr Singh had nearly a two-and-half- hour meeting with the President this evening. An earlier appeal for clemency filed by Memon's brother had been refused by the President last year.
The fresh petition by Memon's lawyers argues that the President can't decide on the mercy plea overnight and should take more time. If accepted by the court registry, a judge will hear the petition at his home.
The Maharashtra government is prepping the final plans to execute Memon, who turns 54 tomorrow. The Mumbai police is making careful arrangements for security.
The Supreme Court today rejected a claim by Memon that he should not hang because proper legal procedure had not been followed in his case.
Memon was first convicted in 2007 by a Mumbai court for planning the attack in which 257 people were killed in serial explosions in the city. The Supreme Court upheld that verdict in 2013. Memon's brother, "Tiger" Memon, and mafia don Dawood Ibrahim, the main masterminds behind the attack, remain missing.
Memon said in the Supreme Court this week that an order to hang him was passed while he still had legal recourse available. Two judges differed on that yesterday, and the case was referred to a three-judge bench today, which ruled against Memon.
Supporters of Memon's plea said he cooperated with investigating agencies. There were reports last week that he surrendered in 1994, choosing to return to India from Pakistan. He had left Mumbai with his family just before the attacks.
Prosecutors and investigators insist Memon was arrested and no secret plea bargain was offered in exchange for his cooperation.
Memon was the only one of 11 people convicted for the 1993 attacks to have his death sentence upheld on appeal. He was found guilty of financing and organising the training in Pakistan of those who executed the attack.
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