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Counties and cities across the United States charge people convicted of crimes for the use of the court system. Some of these fees go to victim restitution funds or to recoup the cost of public defenders, and others for things like DNA testing, fees for a jury trial, or for the cost of housing in jail. 

In practice, the poorest defenders cannot afford these pay-for-use fees, and in some states like Washington, counties chose to imprison these people. This despite a recent advisory from the Justice Department against incarcerating people who can't pay court fees. 

The advisory is not binding, and judges continue to have a great deal of autonomy in determining fees and punishments for nonpayment. Often, these sentences far outlast other punishments, says Alexes Harris, a sociologist at the University of Washington and author of "A Pound of Flesh: Monetary Sanctions As Punishment for the Poor."

"People are convicted. They go to jail or to prison," Harris says, "They have all of these other sentences that they fulfill, but the only sentence they cannot fulfill is paying their fines and fees." 

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