A former federal prosecutor and a Harvard law professor see different weaknesses in both the government’s extortion case against Suffolk County Sheriff Steven Tompkins and his preliminary rebuttal as outlined in a motion to dismiss the prosecution.

A federal grand jury in Boston indicted Tompkins in August on charges of using his official position to pressure a cannabis company to allow him to invest $50,000 before the unnamed company offered stock to the public.

Then, after the value of his investment dipped below $50,000, he demanded and received a full refund of his money, the US Attorney’s Office in Boston alleges.

The indictment accuses Tompkins of implicitly threatening the company’s state license because he could have withdrawn the Sheriff Department’s agreement to screen returning inmates as potential employees at the company’s local store. That arrangement met a state licensing requirement that cannabis operators have a positive impact on communities that suffered most in the war on drugs.

In early October, Tompkins’ attorney filed a motion to dismiss the case, a standard opening gambit of criminal defense lawyers.

Martin Weinberg, a solo practitioner well regarded in legal circles, argued that the sheriff did not commit any official act in exchange for being allowed to invest, noting the agreement to screen inmates came first.

“Mere allegations of ‘fear,’ ‘pressure,’ and ‘demands’ are not sufficient to establish extortion under color of official right,” the motion argues. “Rather, there must be a quid pro quo agreement to exchange an official act for payment, which is lacking here.”

Weinberg’s motion also maintains the indictment overstates any leverage Tompkins could have had because the company’s applications for a license and renewals identified other ways to meet the positive impact requirement.

“It seems like a fairly weak case.

There’s a big difference between having a fairly weak case and getting a motion to dismiss granted,” said Eric Rosen, a former assistant US attorney in Boston who was the lead prosecutor in the college admissions case known as Operation Varsity Blues.

Ronald Sullivan, a Harvard Law professor and criminal defense attorney, said the indictment “makes out a very strong case against Tompkins” but notes motions to dismiss a case rarely succeed. When they do, prosecutors typically return to a grand jury with more evidence and obtain a new indictment, Sullivan added.

Rosen, founding partner of the Boston law firm Dynamis, called it “a fairly weak indictment in terms of the use of fear” by Tompkins to get a refund.

“Is it illegal to ask for your money back? No,” Rosen said. The indictment says a company executive referred to as “Individual A” approved the refund, fearing Tompkins would drop his department’s agreement to screen job applicants.

“All the fear was inside Individual A’s head,” Rosen said. “There’s no detail about what was actually said and when. That part is weak.”

Essential for the prosecution to prove, Rosen said, is “what’s going on in Tompkins’ head. He has to be intending to induce fear.”

Rosen said “Tompkins probably could have made their life difficult” but not stopped the company from renewing its license.

“That’s quite a bit of a stretch.”

Sullivan said the indictment cites the refund to buttress the “central claim” that Tompkins’ stock purchase was “not a standard, run-of-the-mill investment.”

Rosen called that the stronger part of the indictment, raising the question why the sheriff was allowed to invest before the public offering “but for Tompkins’ position as sheriff.”

But Sullivan said recent Supreme Court rulings that a public official’s mere acceptance of a gratuity, an early investment opportunity in this case, does not by itself establish that extortion has occurred. In his motion to dismiss, Weinberg cites one of those rulings, Snyder v. United States, decided last year.

“It’s a hard standard to meet at this stage,” Sullivan said. “Here Sheriff Tompkins has a real case.”

Sullivan added: “It has to be a clear exchange of an official act for some benefit.”

Rosen disputed the motion’s argument that an exchange of an official act for something of value must occur promptly to meet the standards of the Hobbs Act, the federal anti-corruption statute.

“I don’t think you need a quid pro quo right then and there,” he said.

Both Sullivan and Rosen said they expect the Tompkins case to go to trial.

So does his lawyer. “We’re gonna have a trial,” Weinberg told reporters after Tompkins pleaded not guilty at his arraignment but before the motion to dismiss was filed.

Tompkins has stepped aside from his duties as sheriff and resigned as trustee of Roxbury Community College. He was arrested at a conference in Florida but remains free on a $200,000 bond.

The case has been randomly assigned to US District Court Judge Myong J. Joun, whom Joe Biden nominated two years ago. Joun previously served as a judge on the Boston Municipal Court.

Sullivan said the prosecution laid out its narrative of the case in what he called a “speaking indictment.” The motion to dismiss, per standard practice, argues what the prosecution alleges does not amount to a crime.

Weinberg, Sullivan said, would be wise to withhold the defense’s full narrative of the case until closer to the trial, which Weinberg predicted would come in a year or more.

Of the trial, Sullivan said: “It’s gonna be a battle of narratives.”