PORTLAND, Maine — The Portland landlord sentenced to three months for his role in Maine’s deadliest house fire in decades is now seeking a new trial — just days before his jail term is slated to start.

Landlord Gregory Nisbet in October was acquitted of six counts of manslaughter and convicted of one fire code violation, related to the size of the third-floor windows in his Noyes Street duplex. On Monday, his lawyer, Matthew Nichols, filed a motion saying he was not given an important 2013 state document about the size of the windows until after his client was convicted. But the substance of that memo came up in testimony during the trial.

Nisbet was sentenced to 90 days in jail and a $1,000 fine for the single criminal conviction. He now wants the case retried or the single charge dropped.

State prosecutors have 21 days, from the date of filing, to respond to the new motion.

The memo, written by State Fire Marshal Joseph Thomas, says that buildings constructed before 1976 must have windows of at least five square feet and open at least 3.3 square feet. Nichols said in the filing that the third-floor windows in Nisbet’s building were “exactly five square feet.”

“If said memorandum had been provided in a timely fashion, it probably would have changed the verdict in the case,” Nichols wrote in the motion.

But this historic exemption actually came up during the trial. Under cross-examination, Richard MacCarthy of Maine State Fire Marshal’s Inspection and Prevention Division, testified that existing windows in buildings constructed before 1976 were allowed to be five square feet. The court heard conflicting testimony over how wide the third floor windows opened: One witness estimated six inches and another said about one foot.

Nichols did not immediately respond to a request for comment as to whether this testimony has bearing on the request for a new trial.

Thomas argued that the windows on the third floor of Nisbet’s building were too small either way, the Press Herald reported.

During the trial, witnesses recalled hearing screaming from the three people who died on the third floor. A total of six young adults were killed in the accidental 2014 blaze: David Bragdon Jr., 27, Ashley Thomas, 29, and Nicole Finlay, 26, who lived at 20 Noyes St., and visitors Steven Summers, 29, of Rockland, Maelisha Jackson, 23, of Topsham and Chris Conlee, 25, of Portland.

Nisbet is scheduled to begin his sentence on Friday afternoon. He could still file a motion to postpone the sentence while the request for a new trial is evaluated.