Christian Michel, the key accused in the AgustaWestland VVIP chopper case, has filed a petition in the Supreme Court requesting for immediate release from jail, citing right to life and freedom.
Mr Michel, a British citizen, in his petition said he has spent five years and three months in jail, while the maximum punishment in the case, if he is found guilty, is five years.
He said the investigation is not over and the trial has not even started, so his further judicial detention is "illegal".
The Supreme Court will hear the petition on Monday.
The middleman in the AgustaWestland chopper scandal was extradited from Dubai, after his arrest in 2017 in the UAE.
The AgustaWestland case involves a 2007 contract signed by the government to buy 12 luxury helicopters for use by top leaders, including the President, Prime Minister, and former prime ministers.
In 2014, the government scrapped the contract amid allegations that the supplier AgustaWestland, whose parent company was Finmeccanica, allegedly gave bribes in Italy and India.
Former Air Chief SP Tyagi, 72, was arrested in 2016 over allegations that he accepted bribes to tailor specifications at the instance of his cousins. He became the first ever military chief - former or current - to be arrested.
The Congress party has said once talk of kickbacks erupted in Italy, it cancelled the helicopter deal, blacklisted the company and asked the Central Bureau of Investigation (CBI) to look into the scam. It also confiscated the company's assets in India and abroad.
