Prolific international map thief E. Forbes Smiley III is headed into uncharted territory: Smiley—who admitted he stole eight maps from Harvard’s Houghton Library and faces up to 10 years in prison and over $2 million in restitution and fines—is pleading for mercy.

The renowned prowler is asking for leniency, in the form of a sentence no longer than 36 months in prison, even as library officials say Smiley has yet to fess up to all of his thefts.

Smiley, who admittedly stole a total of 97 maps from a number of libraries, submitted a memo to the Connecticut U.S. District Court on Tuesday asking for leniency in the Sept. 27 sentencing proceeding.

But in addition to the eight Harvard-owned maps Smiley has admitted to stealing, there are still five maps missing from Houghton, and Harvard College Libraries spokeswoman Beth Brainard said she thinks Smiley may have taken them.

“I know that Smiley used all the books from which the maps are missing,” Brainard said.

Robert E. Goldman, lawyer for the British Library, was more definite in attributing unresolved map thefts to Smiley.

Although Smiley and his lawyer Richard Reeve were unavailable for comment, the memo they submitted on Tuesday argued that such allegations are “reckless, unsubstantiated, and unfair,” and that “there is little conceivable motive for...[Smiley] to intentionally conceal the theft of other maps at this point.”

But Goldman said Smiley still has “an incentive not to come forward now. [If he revealed additional thefts] the terms of the plea agreement would be null and void and Smiley would face stiffer sentencing guidelines.”

The Harvard College Libraries—along with the other affected libraries—are seeking punishment to the fullest extent of the law, Brainard said.

Goldman and the British Library have gone further—they have advocated an “upward departure” from the sentencing guidelines in light of the fact that “the defendant engaged in a pattern of misconduct involving cultural heritage resources.”

The maximum sentence under the current guidelines would be 10 years, in addition to financial penalties.

In the memo, Smiley indicated that he seeks a sentence of between 30 and 36 months in prison in addition to restitution payments that will total over $2 million.

“We asked the court to impose a sentence that would serve as a deterrent. This case, with an appropriate sentence, can have this effect,” said Goldman.

The Connecticut U.S. Attorney’s office said it will enter its memo regarding the sentencing by the end of the week.

Smiley contended that his full cooperation with the government—he maintained in his Tuesday memo that 40 out of the 97 thefts would not have been realized without his assistance—merits a reduced sentence.

His library opponents disagree and hope to see a stiff sentence handed down on Sept. 27.

“One of the potential harms when a person like Smiley—someone who was trusted, and went on for seven and a half years—is that libraries might limit access to valuable collections out of fear and thus limit future academic pursuit,” said Goldman. “This would be a terrible loss.”

—Staff writer Matthew S. Blumenthal can be reached at mblument@fas.harvard.edu.