It is rare for a municipal judge to submit to questions about his courtroom practices. But in granting an interview this month at his law office in nearby Carrollton, the judge delved into a relatively unexamined question about the legal system today: how to determine whether offenders are unable, or simply unwilling, to pay their penalties.

At a time when many jurisdictions are facing sharp questions about whether they are being overly aggressive in collecting court fines and fees from the poor, and sometimes jailing those who cannot pay, that question is hardly an idle one. The United States Supreme Court has held that the poor cannot be jailed solely for inability to pay a fine. But it has left somewhat open the question of how to determine if they can’t, or won’t.

Civil rights advocates envision a thorough consideration of income, assets, living expenses and debt, and say such hearings rarely occur. Judges, on the other hand, have been known to base their determinations on things like whether the defendant is wearing expensive shoes.

A test like Judge Diment’s — if individuals can pay, they will once threatened with jail, he asserts — is not unheard-of. Nor, for that matter, is jailing those who cannot pay: A new report by the American Civil Liberties Union in New Hampshire found that the state’s taxpayers paid $167,000 in 2013 to jail people who owed $76,000.

The question of ability to pay can be thorny, whether courts decline to consider it or try to do so. In Nashville, where millions in fines have gone uncollected, a special “indigency docket” has raised questions about whether waivers of court debt are too freely granted.