PHOENIX — A federal appeals court has rejected a procedure used by some judges in Arizona to process groups of people charged with entering the country illegally.

In a unanimous ruling Friday, the 9th U.S. Circuit Court of Appeals said judges must address each defendant individually during the part of the procedure where someone pleads guilty. Judge Richard Paez, writing for the court, said that is necessary to ensure each person understands his or her rights and the consequences of the plea.

This is the second time the appellate court has faulted the process, known as Operation Streamline, designed to process as many defendants as quickly as possible so they can be immediately deported.

Jon Sands, the federal public defender in Tucson, acknowledged complying with Friday’s order might result in fewer people being processed. But he said there are good reasons for not rushing.

“We can slow down the process a little bit to make sure due process and the statute is followed,’’ he said.

A spokesman for the U.S. Attorney’s Office said his agency is still studying the ruling and had no comment.

Previously, U.S. Border Patrol agents would question and fingerprint those caught in the country illegally. Those without criminal records or who were not re-entering after previously being deported generally would be granted “voluntary return’’ to Mexico.

The new program, which came to the Tucson Sector of the Border Patrol in 2008, allowed prosecution of anyone arrested on the charge of illegal entry. The aim of the zero-tolerance policy was to convince would-be border crossers that they will have to do jail time if caught.

The ensuing crush of new cases resulted in federal judges and magistrates deciding they could take pleas from entire groups of people at once.

In essence, the judge would ask a single question to an entire group, like whether they all understood their rights, and listen for a general response. It would be up to anyone who did not agree to speak up.

In a 2009 ruling, the appellate court said that does not ensure the judge determines, as legally required, that each person understands.

“No judge, however alert, could tell whether every single person in a group of 47 or 50 affirmatively answered her questions when the answers were taken at the same time,” wrote Judge John Noonan. “No judge could have detected a mute response offered in the midst of a medley of voices saying ‘Si.’ ”

Courts did alter their procedures, but not sufficiently.

In the case before the appeals court on Friday, a magistrate had 63 people in court.

She informed them of their right to a court-appointed attorney, that they had the right to remain silent but would give up that right if they pleaded guilty, the possible penalty, the fact they would be deported after serving their sentence and that if they returned after deportation they could be charged with a felony.

She then called them up in groups of five and asked them if they all understood their rights. The record, through an interpreter, says “all answer yes.” A similar group response came to other questions.

Then, finally, the magistrate directly asked Delcia Arqueta-Ramos if she pleaded guilty, to which the defendant responded, “Yes.”

Paez said there was nothing wrong with advising a large group of defendants of their rights all at the same time. But he said the magistrate ran afoul of legal requirements when she questioned them in groups of five.

“The court accepted ‘all answer yes’ and ‘all answer no’ responses to those questions,” Paez wrote.

The failure to engage defendants in person-to-person speech during the advisement of rights or the subsequent small group questioning, Paez said, violated requirements that a judge “address the defendant personally in open court.”

Sands said the appellate judges got it right, allowing a judge to give defendants their general rights in a group. But differences in individual circumstances may cause someone to want to consider something other than a guilty plea and all that entails, which can’t be brought out in group questioning.

“The person could have been forced to come over,’”Sands said. “The person could be mentally incompetent.”

A call to Judge Raner Collins, the presiding federal judge for Arizona, was not returned.