File photo of Yogendra Chand Upreti

A 74-year-old prisoner at the Gwalior jail has just returned from Delhi where he was taken for treatment for prostate cancer.Yogendra Chand Upreti could soon have a double role as both an accused and a star witness in a scam that is embedded in Madhya Pradesh but forged ahead this weekend into a national shocker with the death of a journalist who was reporting on it and started frothing at the mouth during an interview. The journalist became the 35th person linked to the scam to have died in recent years; the opposition has seized the media attention and national outrage to claim that Chief Minister Shivraj Singh Chouhan, serving his third term, must be removed to allow an impartial inquiry.Top police officers say Mr Upreti can help uncoil the Vyapam scam, named for a state board that conducts examinations for colleges and tests for those who want jobs as government teachers and doctors. Between 2003 and 2004, Mr Upreti was the head of the board. On his watch, say investigators, students found willing conspirators in politicians and bureaucrats to help them land prize posts in educational institutions and government departments. For a price, of course.Mr Upreti was arrested in June. Since then, investigators say, he has detailed the crude but effective processes that drove the scam, encouraging them to think of turning him into a star witness.This is what he has reportedly disclosed: Those who passed the tests would be paid to refuse their place in colleges; they would cite reasons like not being able to afford the fee. Often, those students who took and cleared the tests were allegedly hired hands from the very start - they were chosen because they were certain to crack the exam; the conspirators therefore knew exactly how many places would be available for sale. Sometimes, a place in a medical college would be sold for as much as 35 lakhs; a post-graduate spot could cost a crore.Mr Upreti is accused in one of the nearly 60 criminal cases of the Vyapam investigation conducted by the Madhya Pradesh police. But his real value for interrogators lies in the information he has disclosed."Upreti is an important witness," said Ashish Chaturvedi, a 26-year-old and one of four whistleblowers who helped expose the Vyapam scam. "He will be able to shed light on many VIPs linked to the case, which is why he should be carefully protected," he said to NDTV.The earliest cases of cheating and impersonation for exams conducted by Vyapam date back to 2000, before the BJP or Mr Chouhan came to power in 2003 But the scale of the misdoings surged by 2009, and it was in 2013 that the police assigned a task force to handle the probe.