Immigration and Customs Enforcement headquarters in Washington. (Salwan Georges/The Washington Post)

LAST FRIDAY night, a 7-year-old Congolese girl was reunited with her mother in Chicago, four months after immigration agents of the Department of Homeland Security separated them for no defensible reason. When the little girl, known in court filings as S.S., was delivered by a case worker to her mom, the two collapsed to the floor, clutching each other and sobbing. According to the mother’s lawyer, who was in the room, S.S., overwhelmed, cried for the longest time.

That sounds like a happy ending to a horrific story. In fact, according to immigrant advocates, such separations are happening with increasingly frequency — with no credible justification.

In the case of S.S. and her mother, known in court filings as Ms. L., the trauma visited on a little girl — wrenched from her mother, who was detained in San Diego, and flown nearly 2,000 miles to Chicago — was gratuitous. A U.S. official who interviewed Ms. L. after she crossed the border into California determined she had a reasonable asylum claim based on fear for her life in her native Congo. Despite that, mother and daughter were torn apart on the say-so of an immigration agent, and without explanation.

A DHS spokesman, Tyler Houlton , says separating children from their parents is justified when paternity or maternity is in doubt, or when it is in a child’s best interest. However, in court filings, officials present no cause for doubt about Ms. L.’s maternity, nor evidence that it was in S.S.’s “best interest” to be taken from her mother last November, when she was 6 years old.

Rather, in court filings, an official from Immigration and Customs Enforcement, a DHS agency, lists some documentary discrepancies on Ms. L.’s part, in which officials in Angola, Panama and Colombia recorded different versions of her name. Never mind the translation problems she may have encountered in Latin America as a speaker of Lingala, a language spoken only in central Africa.

Even if Ms. L. fudged her identity, how would that justify taking away her child? And if there were doubts about Ms. L.’s maternity, why didn’t ICE request a DNA test at the outset, before sundering mother and child? When a DNA test was finally done — four months later — it immediately established Ms. L.’s maternity.

Immigrant advocates say DHS has separated children from immigrant parents scores of times in recent months, perhaps to deter other asylum seekers by trying to convince them the United States is even more cruel than their native countries. Officials at DHS have floated that idea publicly in the past year. They insist it is not their policy. However, they also have declined to provide statistics showing the frequency of separations.

Responding to a class-action lawsuit filed by the American Civil Liberties Union on behalf of parents separated from their children, ICE insists it has done nothing so outrageous that it “shocks the conscience” — a Supreme Court standard for measuring the denial of due-process rights.

Here’s a question for Homeland Security Secretary Kirstjen Nielsen: If it does not “shock the conscience” to traumatize a little girl by removing her from her mother for four months in a land where she knows no one and speaks no English, what does “shock the conscience”?