An inmate at the D.C. jail last year. (J. Lawler Duggan/For The Washington Post)

THE NATIONAL Registry of Exonerations declared Wednesday that “by any reasonable accounting, there are tens of thousands of false convictions each year across the country, and many more that have accumulated over the decades.”

In truth, the registry, based at the University of Michigan Law School, cannot tell for sure how many. Yet the figures and trends its researchers have fully documented are chilling enough. In a new analysis, the registry reports that at least 149 people were exonerated last year, a record that represents a large increase from just a few years ago. Certainly there must be many other innocents behind bars who cannot provide proof.

Twenty-seven of last year’s exonerated convicts gave false confessions, mostly in homicide cases. Most were mentally ill or were minors at the time of confession. Meanwhile, 65 people were exonerated despite having pleaded guilty. Most of these pleas came in drug cases — in some of which no crime even occurred.

The researchers found that only 17 percent of last year’s exonerations were due to DNA evidence, and they documented only 65 instances of official misconduct, mostly in homicide cases. These figures imply another sort of unacceptable error: of honest police, prosecutors and juries failing to give defendants the presumption of innocence, as the law requires.

Observers tend to focus on exonerations from death row, and there were five last year. But a long prison sentence or having a criminal record after release can shatter people’s lives, too.

The adversarial justice system, in which one lawyer throws everything at the other and lets a judge or jury sort it out, encourages each side to take maximalist positions and bargain from there. This can lead prosecutors, who hold tremendous power, to cross the line between determined and zealous. Plea bargaining helps keep the machinery of the criminal-justice system moving, but the system can put far too much pressure on defendants to forgo their day in court.

One relatively easy reform is for law enforcement to test confiscated substances to ensure they are bona fide illegal drugs before prosecutors offer a plea bargain on a drug charge. In some places, conviction integrity units are becoming important tools for encouraging professionalism — or exposing its absence. The integrity unit in Harris County, Tex. — the home of Houston — exposed 43 of Texas’s 54 exonerations last year. There are 24 such units across the country, four times as many as there were in 2011, but still only about 15 percent of Americans live in places that have such units.

Moreover, these watchdogs need to feel free to challenge prosecutors’ work, but that can be hard when they are housed within local prosecutors’ offices. North Carolina pursued another option: an independent, state-level commission that examines convictions and reports to a review board. Other state legislatures should consider establishing similar oversight bodies.

“We’ve made a start,” the registry’s report says, “but that’s all.”