Jayarajan, Kannur district Secretary of CPI(M), was shifted to the hospital following the advise of doctors who checked him at the Kannur Jail.
CBI had in January listed Jayarajan as an accused and framed charges against him under Unlawful Activities (Prevention) Act in connection with the case.
Manoj (42), an RSS district functionary, was hacked to death in politically-volatile Kathiroor in Kannur district on September 1, 2014, allegedly by a group of CPI(M) workers.
Meanwhile, the District Sessions Judge V K Anilkumar deferred the decision on Jayarajan's bail application for tomorrow.
The arguments over the bail plea before the court had been completed on Saturday last.