The author of a sweeping new U.N. study on the detaining and jailing of children worldwide acknowledges that he erred in saying the U.S. is holding more than 100,000 children in migration-related detention. The author, human rights lawyer Manfred Nowak, says he wasn't aware at the time that the number was from 2015. He adds that it reflected the number of children detained during the entire year.

Nowak acknowledges that his use of the statistic was misleading, but he also maintains that his main point about the U.S. having high incarceration and detention rates for children still stands. In an interview with NPR on Wednesday, he said he was citing a number from the U.N. High Commissioner for Refugees.

"I used the UNHCR data because it was the last UNHCR figure that was published, and that goes back to the year 2015," Nowak said. "And I haven't checked it that clearly in the press conference. So that was, of course, misleading."

Nowak mentioned the number on Monday, as he discussed the U.N.-sponsored Global Study on Children Deprived of Liberty at a news conference in Geneva.

Referring to children who were detained by the U.S. after arriving at the border either unaccompanied or with their parents, Nowak said earlier this week:

"The United States is one of the countries with the highest numbers. We have more than, still more than 100,000 children in migration-related detention in the United States of America. So that's far more than all the other countries where we have reliable figures."

His comments were reported Tuesday by multiple news outlets, including NPR, which removed its story when Nowak's error became apparent.

Revelations that the U.S. detention statistic dated to the Obama administration drew intense attention because as he spoke about the detention figure, Nowak also pointedly criticized the Trump administration's policies of separating children from their parents at the border.

"I would call it inhuman treatment for both the parents and the children," he said on Monday, adding that he believes the policy runs afoul of several international civil rights treaties.

In the U.S., children who arrive at the border unaccompanied are placed in the custody of the Department of Health and Human Services, through its Unaccompanied Alien Children program and the Office of Refugee Resettlement.

HHS says that over the 2019 financial year, approximately 69,550 unaccompanied children were referred to the UAC program. In its most recent news release about the number of minors in its care, the agency adds that since 2012, "this number has jumped dramatically."

HHS currently has approximately 3,900 children in its custody through the UAC program, the agency says in an email to NPR.

"The system-wide average length of care for minors discharged from ORR in the month of September 2019 is 57 days, down from the recent high of 93 days in November 2018," the agency says.

HHS also lists the number of children it has unified with a sponsor in recent fiscal years, under both the Trump and Obama administrations:

When asked about the latest HHS figures, Nowak says, "So perhaps it's really down now to 69,000. That's fine — but again, it's much higher than other states that detain children in migration-related detention. So it's still the highest number. So I think the main message remains the same."

As for how he came to quote data from 2015 — the year before he was selected to lead the U.N.'s global study on child detentions — Nowak said he was trying to answer one of the first questions at Monday's news conference, which focused on the U.S. detention of children as part of its migration policies.

"I received quick info from my assistant, where he said that's the latest data that we have," Nowak says. "But I didn't know at that moment that it was [from] 2015. If I would have known that, I would not have mentioned it, because that's some time ago."

The 2015 statistic does not appear in his global study's section on the U.S., Nowak notes. And he adds that he stands by the figures that are compiled in his report.

"Whatever you read in the report is definitely accurate," Nowak says, adding, "we really checked it very, very well."

To compile the study, Nowak and his researchers sorted through official records and statistics from advocacy groups and countries' replies. They also sent out questionnaires. Nowak said on Monday that the U.S. didn't respond to his team's official requests for data — but he added that many of the numbers they were seeking were publicly available.

The global study's release coincides with the 30-year anniversary of the adoption of the U.N. Convention on the Rights of the Child. The U.S. signed the agreement but never ratified it; today, the United States is the only country in the world that has not ratified the U.N.'s treaty on children's rights.

The study includes a key paragraph about the U.S. policy of detaining children in the process of enforcing migration laws, referring to a span that includes both the Trump and Obama administrations:

"In the United States, in a period of 3 years, between 2013 and 2015 immigration authorities detained 278,885 children. Apprehensions (and detention) of children reached a peak between October 2018 and August 2019, the first 11 months of the fiscal year 2019 (fiscal year, FY), when US Customs and Border Protection (CBP) apprehended 72,873 unaccompanied children and 457,871 members of 'family units' at or near the US-Mexico border. Between 2013 and 2018, the annual number of apprehensions of unaccompanied children varied between ca. 39,000 and ca. 69,000. The annual number of apprehensions of 'family units' varied between ca. 15,000 and 107,000 annually."

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