Just before Christmas, Janice Dotson-Stephens died in a San Antonio jail. The 61-year-old grandmother had been arrested for trespassing, a class B misdemeanor in Texas. She couldn’t afford the $300 bail, and a mere $30 payment to a bail bondsman would have let her out. She stayed in jail for nearly five months, waiting for her case to be handled, before she died. Her family has sued, and an independent agency is currently investigating the cause of her death. This is how the American misdemeanor system quietly and carelessly ruins millions of lives.

Dotson-Stephens was a victim of a vast misdemeanor machinery that routinely and thoughtlessly locks up millions of people every year. America is already infamous for mass incarceration — with 1.5 million state and federal prisoners, we put more people in prison than any other country on the planet. But nearly 11 million people pass through over 3,000 US jails every year, according to a 2016 report by the Department of Justice. On any given day, there are approximately 700,000 people in jail. One-quarter of them are there for misdemeanor offenses; the majority of them, like Dotson-Stephens, have not been convicted of anything and are therefore presumed innocent.

Given the minor nature of most misdemeanors, it is shocking how often they send people to jail. Amazingly, people routinely get locked up when they are arrested for petty offenses even if they could not be sentenced to jail for the offense itself.

Albert Florence was arrested in New Jersey for failing to pay an outstanding civil fine, a transgression for which he could not have been incarcerated. Nevertheless, he spent six days in jail where officials strip-searched him twice, inspected his genitals and subjected him to a delousing shower. Turns out it was a mistake — Mr. Florence had paid the fine years before but the statewide database had not been updated.

Was this legal? It was. When the US Supreme Court heard Florence’s case in October 2011 in Florence v. Board of Chosen Freeholders of County of Burlington, it decided in April 2012 that the strip searches were constitutional.

The most common punishment for a misdemeanor conviction is probation and a fine, but jail remains routine. In Richmond, Virginia, Robert Taylor, an indigent veteran, was sentenced to 20 days in jail for driving on a license that been suspended multiple times because he could not afford to pay traffic court fines. In Beaufort County, South Carolina, a homeless man spent 30 days in jail and was sentenced to time served for the charge of trespassing at a McDonald’s.

Poverty isn’t a crime, but the misdemeanor machinery often treats it like one, incarcerating people solely because they cannot afford to pay a fine or fee. In Augusta, Georgia, Tom Barrett was homeless, living off food stamps and the money he earned from selling his blood plasma. He was caught stealing a $2 can of beer. He couldn’t afford the $50 fee to apply for a public defender, so he represented himself, pleaded guilty and was placed on probation. As part of that probation, he was required to pay over $400 in fines and fees every month. When he couldn’t, he was sentenced to 12 months in jail. “I should not have taken that beer. I was dead wrong,” says Barrett. “But to spend 12 months in jail … it didn’t seem right.”

In Woodworth, Louisiana, Patricia Parker was a cook at the Methodist Conference Center. As a result of four contested traffic violations, she was arrested in front of her children and spent 25 days in jail for failing to pay fines and fees. Woodworth has been declared one of Louisiana’s top speed traps; the city collects 61 percent of its budget from traffic tickets.

The misdemeanor system is enormous. Thirteen million misdemeanor cases are filed every year — that’s 80 percent of state criminal dockets. This is how the American criminal system works most of the time for most people. And its tendency to incarcerate affects millions of families — over 400,000 children have a parent in jail, and more than half of all Americans have seen a member of their extended family incarcerated, according to a joint research report, “Every Second: The Impact of the Incarceration Crisis on America’s Families” by FWD.us and Cornell University.

The misdemeanor phenomenon has been largely overlooked, overshadowed by the sheer harshness of its felony counterpart. And some of that is fair enough. Thirty-year drug sentences, solitary confinement and the death penalty do indeed make misdemeanor punishments seem petty. But make no mistake, they are not lenient. People are being stripped of their liberty and their money. If we really want to roll back mass incarceration and improve our criminal system, we need to shrink the massive misdemeanor pipeline and break its expensive and destructive habit of putting people in jail with so little justification.

Alexandra Natapoff is a law professor at the University of California, Irvine, and author of “Punishment Without Crime: How Our Massive Misdemeanor System Traps the Innocent and Makes America More Unequal” (Basic Books), out now.