The son of dead Russian laser scientist Dr Dmitry Kolker, 54, today accused Vladimir Putin's FSB security service of killing his father.
The world-class expert was removed from a drip at a cancer hospital on June 30 and flown from Siberia to Moscow under suspicion of spying for China.
He was being held on suspicion of high treason by the FSB counterintelligence agency, once headed by Vladimir Putin.
The family had warned the intelligence service that he was on his deathbed, too ill with pancreatic cancer to face further chemotherapy.
After being flown to Moscow, he was put inside the notorious Lefortovo prison before being rushed to the hospital where he died early on Saturday.
"The FSB killed my father, knowing his condition, they didn't even let our family say goodbye," said Maxim Kolker, 22.
He blamed the spy case investigator – who he named as Morozov – along with the Novosibirsk judge who approved his father's detention and "the entire state machinery".
Dr Kolker was one of two leading academics accused of being in a Chinese spy ring.
The other, Professor Anatoly Maslov, 75, a pioneer of hypersonic technologies, remains in Lefortovo jail in Moscow, where Dr Kolker was held before being rushed to a hospital where he died.
Dr Kolker's family accused Putin's security services of "torture" and human rights abuse in seizing the top scientist on his death bed.