Harding faces 47 charges of criminal negligence — one charge for each person that was killed in the derailment explosion last July.
Harding's lawyer, Tom Walsh, told CBC's French-language counterpart Radio-Canada that he's concerned the unsealed documents could sway a jury.
"The state has the obligation of ensuring every individual has a fair trial, and they certainly have no obligation, or no right to go out and muddy the water, the way they've done here,” Walsh said.
The court documents were made public by a Quebec judge two weeks ago and were published by several media outlets, including CBC News.
The documents, originally submitted to a judge by police almost a year ago, permitted police to obtain a search warrant for Montreal, Maine & Atlantic Railway offices.
They contained statements from witnesses, including a summary of Harding's account of that night.
The documents revealed that Harding said he only applied seven manual handbrakes after a routine stop in Nantes — before the derailment took place.
MM&A's rules would have required at least nine handbrakes.
Walsh would not comment on the specific allegations because he did not want to harm his client's case, but he did say the published documents don't tell the whole truth and that Harding's version included more details and nuances.
Walsh was astonished when he found out the information had been released to the public, and wonders if his client will be able to get a fair trial.
"It will at least complicate things. We're already going to have enough trouble to find 12 English-speaking people who have not read or heard any of those very unnecessary revelations,” Walsh said.
He is demanding an explanation from the Crown.
The director of criminal and penal prosecutions of Quebec refused to comment on the case because it is before the courts.
Walsh hasn’t ruled out the possibility of asking for a stay of proceedings.