In early April, a machine from Delhi University containing cobalt-60, a radioactive metal used for radiotherapy in hospitals, ended up in a scrapyard in the city.
Rajendra Yadav, a 35-year-old worker in the congested yard in Mayapuri, western New Delhi, died due to multiple organ failure on April 26.
Seven others were hospitalised.
The International Atomic Energy Agency (IAEA) said it was the worst radiation incident worldwide in four years.
Yadav had been given a "shiny piece of a white metal" from the machine as a sample to scout for a buyer and had carried it around in his leather wallet, showing it to potential customers.
In pain and with burn marks on his hips and thighs, he went to see doctors who confirmed he had suffered radiation poisoning, sparking panic in nearby residential areas and leading to a scramble for the source by investigators.
"The metal was gleaming. We assumed it to be expensive and wanted to sell it for a good price," said Yadav's friend, Deepak Jain, wh