Cook County Chief Judge Timothy Evans is refusing Chicago Mayor Lori Lightfoot’s request to halt the release of pretrial defendants charged with certain crimes and saying the data she has used to press for that change is flawed.

Evans’ office said he sent a letter Tuesday criticizing the request, a response by Lightfoot to the city’s 20-month-old gun violence surge, which lifted last year’s homicide total to 836, the most in a quarter century. The chief judge is opposing Lightfoot’s drive for a “temporary moratorium” on releasing defendants on electronic monitoring, known as EM, if they face offenses including murder, attempted murder, aggravated battery, sex crimes, carjacking, kidnapping and illegal weapons possession.

“There is no evidence that individuals released from pretrial detention are driving this wave of violence,” Evans’ office said in a Tuesday statement that described his letter to Lightfoot. “Since the beginning of the COVID-19 pandemic, [the violence] has struck both cities like Chicago that have undergone bail reform and cities that have not.”

Bail reforms in 2017 and pandemic responses in 2020 allowed more people in Cook County to wait for their trial wearing a GPS-enabled ankle bracelet instead of sitting in jail. The county’s main EM program, run by Sheriff Tom Dart’s office, requires the defendants to stay home unless they have court-approved permission to leave for work, school or job-skills training. The sheriff’s daily EM population last year averaged around 3,300, up from about 2,200 four years earlier, according to his office.

Lightfoot’s moratorium request includes the weapons possession charges even when the defendant has no criminal background. At a Jan. 4 news conference, she described those offenses as “gateways” to more serious crimes.

In a Dec. 29 letter to Evans, Lightfoot urged the chief judge to “consider the effect on victims, witnesses and survivors of having violent, dangerous people right back on the streets within days of their arrests.”

“Imagine if you are someone who has been victimized by gun violence and you summon the courage to provide law enforcement with information that leads to the arrest of the person(s) responsible,” the mayor wrote to Evans. “Then within 24-48 hours after the arrest, that same person is back on the streets with virtually no restriction of movement. Would any of us feel safe in that scenario? What message does it send to the victims, witnesses or survivors?”

But Evans, who released only portions of his letter responding to Lightfoot, pointed to constitutional problems with keeping people in jail based on accusations by police: “In our justice system, the accuser is not the adjudicator. A judge, not a prosecutor or law enforcement official, must decide whether an individual shall be deprived of his or her liberty.”

Evans’ office said most defendants charged with murder or attempted murder in the county are already in jail. Of people charged with either of those offenses between October 2019 and September 2021, 86% were not released and had to spend the duration of their case behind bars.

Looking at all the offenses that Lightfoot wants an EM moratorium to cover, Evans’ office said thousands of defendants had those charges dropped during the 2019-2021 span because of insufficient evidence or were found not guilty at trial.

“Those who were detained in jail but not convicted were deprived of liberty without having been found guilty of the charges and were unable to pursue education, work, or support their families while in jail,” the statement from Evans’ office said.

“The law requires that defendants shall be released on the least restrictive conditions that will reasonably ensure they will appear in court and that will reasonably protect the community, witnesses, victims or any other person,” the chief judge’s office said.

Evans also pointed to inaccuracies in the data that Lightfoot has highlighted to build support for her proposal. Those include 15 individuals the Chicago Police Department listed as being on electronic monitoring when picked up on a new murder charge last year. Evans’ office said at least five of those new arrests were for killings that happened in 2020 — before the suspect was released with the ankle bracelet.

A sixth defendant on that list, according to the chief judge’s office, was put on EM for a violent offense and then arrested on murder charges stemming from the same incident, not for a new crime.

Evans’ office said that, among other new arrests in Lightfoot’s data, his staff found defendants whose top charge leading to the EM had been a nonviolent drug offense. The chief judge’s office said it found others in the mayor’s data who were not on EM at the time of their arrest.

The chief judge’s qualms with Lightfoot’s data follow similar findings by the Chicago Tribune.

Evans has also pointed to academic studies that have found that the vast majority of people facing gun-related charges and released on EM in Chicago are not arrested for a new crime as their case plays out and that weapons possession offenses by the EM population represent just a tiny fraction of the city’s gun arrests.

Lightfoot’s proposed EM moratorium has also drawn criticism from State’s Attorney Kim Foxx.

“This narrative around electronic monitoring has been a constant refrain for almost 18 months,” Foxx told WBEZ. “It’s unfortunate because it has added fear that is misplaced and takes us away from dealing with the real issues that are driving violence.”

Those issues, Foxx said, include gun accessibility and long-term disinvestment from communities.

Dart, the sheriff, has voiced concern that the EM program he oversees includes people charged with violent crimes but, at an online forum with North Side politicians this month, he said his office has data showing that “the vast majority of the people [on EM] that we have — even the violent people — are not recommitting offenses.”

“The technology is very good,” Dart said. “When there is a movement that [defendants on EM] are not supposed to do, we contact people, see if there’s a reasonable explanation. If not, then we send [sheriff’s] cars over there.”

While Lightfoot’s letter focused on defendants in Dart’s EM program, she urged Evans to release figures about a smaller EM program that the chief judge supervises.

Evans’ office, exempt from the state’s open-records law, has not answered WBEZ questions about how many defendants his EM program involves, the charges they face or the number who were rearrested last year while in the program.

Lightfoot’s office did not immediately release the letter from Evans or respond to a request for comment about it.

Chip Mitchell reports out of WBEZ’s West Side studio about policing. Follow him at @ChipMitchell1. Contact him at cmitchell@wbez.org.