If successful, a formula would be used to work out the payout amount, which would include "loss of remuneration for those 13 years, pain and suffering and disbursements paid out,'' said Williams.
"I would say the amount must be in excess, well in excess of $2m.''
Williams helped free Arthur Allan Thomas, who received $1m compensation for his lost nine years in prison after being wrongly found guilty of murder.
The case resulted in changes to the conduct of trials and judicial system reforms, said Williams.
Bain's compensation case has taken a step forward with Justice Minister Simon Power announcing this week retired Canadian Supreme Court Judge Justice Ian Binnie would hear the case, due to its long-running and high-profile nature.
Justice Binnie has been a Supreme Court judge for more than 13 years, was appointed a Queen's Counsel in Ontario in 1979 and was Canada's deputy justice minister from 1982 to 1986.
Appointing an offshore Justice for the case was a positive move, said Williams.
Barrister Colin Withnall QC agreed.
"Well it's progress - things moving, and that's got to be good in itself. I'm pleased to see some recognition from the powers that be that this is no ordinary case,'' he told the radio station.