In 1983, there was a significant ruling made by the Supreme Court. The ruling echoed something that had already been done more than 100 years prior to it -- namely that debtors' prison, which is the idea that a person who can't pay his or her court costs and fines should be jailed, are illegal. But there was a stipulation in the ruling that said if a person had the financial means to pay the fees and fines but refused to pay, then he or she could be thrown in jail.
This stipulation has given rise to what amounts to the figurative reinstitution of debtors' prison. In order to determine if a person is willfully refusing, it is left up to a judge to decide. Judges don't always get this right, because it is inherently a subjective decision. No one would be immune to making a mistake if they were in the judge's chair.
However, it raises the question of whether we should be tossing people in jail for failing to pay their court fees and fines. Obviously by the letter of the law, it can't happen except under specific circumstances. But those circumstances are being applied much more regularly.
Court fees, fines and penalties are used far more frequently nowadays, and more people are unable to pay them off. Combine these two factors and we are seeing the inevitable rise of debtors' prison cases. People who are accused of crimes and have financial obligations that are associated with these crimes need to consult their criminal defense attorney to make sure they are compliant. If their financial situation makes this impossible, then they should still talk to their lawyer to ensure they are going about the criminal process properly.
Source: NPR, "Unpaid Court Fees Land The Poor In 21st Century Debtors' Prisons," Renee Montagne, May 20, 2014