NEW DELHI: Union law minister Ravi Shankar Prasad said Friday was a day of satisfaction with Nirbhaya getting justice , but also time to introspect whether death-row convicts could be allowed to "manipulate" system to delay execution.The four men -- Mukesh Singh (32), Pawan Gupta (25), Vinay Sharma (26) and Akshay Kumar Singh (31) -- convicted for the 2012 gang rape and murder of the 23-year-old physiotherapy intern, who later came to be known as 'Nirbhaya', were hanged at 5.30 am inside Delhi's Tihar Jail."It's a day of satisfaction that a daughter, who underwent so much pain, has got justice," Prasad told reporters in Parliament premises. "It's time for judiciary, government and civil society to introspect whether death-row convicts can be allowed to manipulate system and cause delay."