The wrongful conviction of Ronnie Long might appear shocking: No physical evidence, false testimony, a conflicting description of the suspect — then 44-years in prison for Long.

But experts and advocates aren't surprised: They say U.S. prisons are filled with potentially thousands of innocent people. While Long's case is particularly egregious, experts told USA TODAY some of the factors that led to his imprisonment are still causing wrongful convictions today.

The 68-year-old Black man, who is set to receive a historic $25 million settlement, was convicted by an all-white jury for the rape of a white woman, according to his attorneys. Evidence that could have exonerated Long was not shared with the defense and police officers gave false testimony during the trial, according to Duke Law School's Wrongful Convictions Clinic. Despite Long not matching the victim's original description of her assailant, the prosecution relied on the victim’s identification of Long as their main piece of evidence.

"When you take a look at the role that race and official misconduct played in Ronnie Long's wrongful conviction, this is unfortunately common practice in our criminal legal system," said Vanessa Potkin, the Innocence Project's director of special litigation. "So it's not an outlier."

How many wrongfully convicted people are freed in the US every year?

Since 1989, more than 3,400 people have been exonerated of crimes they did not commit, according to the National Registry of Exonerations. Those wrongfully convicted people spent more than 31,000 years in prison.

The number of exonerations has also grown by almost 70% since 2017 — 3,200 compared to 1,900 — the registry said in its 2022 report on wrongful convictions in the United States.

Maurice Possley, a senior researcher at the National Registry of Exonerations, said the recent uptick is driven in part by cases like that of Chicago police Sgt. Ronald Watts, who charged people in and around a since-demolished housing project with crimes they did not commit. Since 2016, prosecutors have moved to vacate at least 226 convictions and juvenile adjudications connected to Watts and his team.

Potkin said this increase is also likely caused by the growth of organizations like the Innocence Project and specialized units in prosecutors offices, which directly address this issue. Still, she said, "exonerations are not keeping pace with the problem by any means."

How many innocent people are still in prison?

It's almost impossible to know how many of the nearly 2 million people imprisoned in the United States today are innocent, said Jamie Lau, a clinical professor at Duke Law School and supervising attorney of the school's Wrongful Convictions Clinic.

In 2011, Mother Jones estimated 1% of the U.S. prison population were falsely convicted, an extrapolation based on known DNA exonerations in the U.S. since the late 1980s. That number may be even higher for people who have been sentenced to death: Researchers in 2014 estimated that if all defendants facing a death sentence remained on death row indefinitely, at least 4.1% would be exonerated.

"Whether it's even 1%, it's a staggering high number of people that I just think anybody that does this work finds totally unacceptable," said Lau, who served as Long’s lead attorney during the appeal that led to his exoneration. "Hearing that number, if you think of the prison population and just 1% of that population, we're talking about thousands of people wrongly incarcerated."

What have been some of the most egregious recent wrongful conviction cases?

• In December, Glynn Simmons was exonerated in Oklahoma after spending 50 years in prison for murder. Simmons' attorneys said evidence showed eyewitness, who had survived being shot in the head during the robbery, did not actually initially identify Simmons.
• Also in December, Marvin Haynes, 36, had his 2004 murder conviction vacated in Minnesota after serving 19 years of a life sentence. Hennepin County Judge William Koch said in his ruling the evidence was unreliable and "constitutionally improper." Koch added Haynes didn't match the description of the suspect given by primary eyewitnesses as he was significantly younger, shorter and weighed less.
• In September, Gerardo Cabanillas, of California, was released from prison after serving 28 years of a life sentence for a 1995 sexual assault, robbery and kidnapping. Police couldn’t find evidence linking him to the crime and prosecutors used a coerced confession and eyewitness identifications.
• In August, Rosa Jimenez was exonerated two years after a state appeals court said false and misleading testimonies led to her murder conviction. Jimenez was sentenced for the death of a 21-month-old who died months after ingesting a mass of paper towels.

Why are people wrongfully convicted?

The National Registry of Exonerations tracks six common contributing factors that lead to a wrongful conviction: official misconduct, perjury or false accusation, false or misleading forensic evidence, false confession, mistaken witness identification and inadequate legal defense. Possley said the most common factors are official misconduct and perjury.

Black people comprise 53% of the 3,200 exonerations listed in the registry, making African Americans seven times more likely than their white counterparts to be falsely convicted of serious crimes, according to the organization's report. Potkin said that racial disparities in wrongful conviction mirror disparities seen throughout the criminal justice system including policing, jury selection and pretrial detention.

"It's just harder for people of color to get relief and easier to be wrongfully convicted in the first place," she said.

Contributing: Grace Hauck, USA TODAY