Anwar Ibrahim has spent five years in jail on a corruption charge and is seeking bail while awaiting the outcome of an appeal against a conviction for sodomy.
Court of Appeal judges have told Anwar's lawyers they expect to make a decision on Wednesday.
They have been considering the case since argument ended on last July after a hearing which began last April.
"He has been beaten and denied medical care, he was forced to sit through a trial that made a mockery of justice," said Brad Adams, executive director of Human Rights Watch's Asia division.
"Releasing Anwar would end the injustice he's suffered and signal a renewed spirit of independence for Malaysia's judiciary."
Former Malaysian prime minister Mahathir Muhammad sacked the charismatic and popular Anwar in 1998 and he was later sentenced to a total of 15 years in prison.
Anwar says the charges were trumped up to prevent him from making a challenge for the premiership.
He wants to travel abroad for treatment for a slipped disc in his back, which he says was injured by a police assault when he was first arrested.
Anwar appeared in court Monday in a wheelchair and wearing a neck brace.