Special Judge Narottam Kaushal also discharged Sudheendra Kulkarni, close aide of BJP senior leader L.K. Advani, and BJP activist Sohail Hindustani.
However, the court framed corruption charges against Sanjeev Saxena, Amar Singh's former aide.
On July 22, 2008, Bharatiya Janata Party (BJP) MPs Faggan Singh Kulaste, Mahavir Bhagora and Ashok Argal waved wads of currency notes in the Lok Sabha ahead of a trust vote, alleging they were given the money to vote in favour of the Manmohan Singh government.
In its first charge sheet filed in August 2011, the Delhi Police had accused Amar Singh and Sudheendra Kulkarni, close aide of senior BJP leader L.K. Advani, of conspiring and masterminding the cash-for-vote scam to bribe some MPs ahead of a confidence vote in the Lok Sabha July 22, 2008.
In 2009, the case was registered on the recommendation of a parliamentary panel which had probed the scam.
All the accused were booked under various provisions of the Prevention of Corruption Act and for criminal conspiracy under the Indian Penal Code.
Argal, Kulaste and Bhagora had earlier claimed it was a sting operation to highlight horse trading in parliament, ahead of the July 22, 2008 trust vote.