Here’s another appalling angle to the United States’ cruel crackdown on immigrants: The government has no real plan for how to reunite the parents and children separated at its southern border. But it’s scrambling to meet a legal deadline to do so – which is why, on Thursday, Health Secretary Alex Azar announced that his agency is taking DNA samples from the kids, to try and match them up with their loved ones.

This is grossly unethical – in the words of Jennifer Falcon, “how can a two-year-old agree to this?” Ms. Falcon is the communications director of the largest immigration legal organization in Texas, RAICES, which last week declined an offer from personal genomics company 23andMe to attempt to reunify families through DNA.

“These are already very vulnerable communities, and this would potentially put their private information at risk,” Ms. Falcon told NPR affiliate station KQED at the time. “Essentially, we’re solving one violation of their civil rights basically with another.”

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Collecting the most personal information possible from minors is an ethical non-starter. Genomic data have the potential to work miracles in medical care and law enforcement, but informed consent must be the bedrock of participation.

That must include a real ability to say no.

Leon Logan didn’t feel he had that choice when his DNA was taken by the Ontario Provincial Police. A Jamaican national, Mr. Logan was working as an apple picker in Bayham, Ont., in 2013 when a local woman reported being sexually assaulted.

Her description of her assailant was detailed: a man in his mid to late 20s, 5-foot-8 or -9 inches tall, with black skin. Yet aside from darker skin tones, many of the 100 men who police requested cheek swabs from didn’t match the profile. The shortest was 5 foot 1, the tallest 6 foot 5. The oldest was 68, four decades older than the perpetrator.

Like Mr. Logan, all were here as temporary migrant workers, their immigration status dependent on pleasing their employers.

“The reason why I did it, I thought I wasn’t going to come back on the program if I didn’t,” Mr. Logan said in a phone interview this week. He wasn’t wrong to feel coerced: Only two workers refused to give a sample, and one hasn’t received a work contract since. The other turned out to be the assailant, his DNA collected from a cigarette butt.

DNA held in the national databank used by Canadian law enforcement belongs to either convicted offenders or crime scenes. But although the Bayham migrant workers’ actual DNA has been destroyed, their genetic profiles have been retained for the past five years, even though none was ever accused of the crime.

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They want those destroyed, too, but so far haven’t had any luck. They went first to the the civilian board that reviews complaints against police in Ontario, but in 2016 it ruled that the Bayham DNA sweep was not an example of racial profiling.

Now, one group of the migrants is putting together a class action suit alleging their Charter rights have been violated, while Mr. Logan and 53 other men are going through the Human Rights Tribunal, citing discrimination. Movement in either case will take at least a year.

Law enforcement is increasingly positioning DNA as a magic tool. In April, California police arrested a man suspected to be the infamous Golden State Killer, responsible for a string of violence dating back 40 years. Using a technique known as “familial searching,” investigators uploaded crime scene DNA to a public genome databank, then built a family tree to identify possible suspects.

But the one they arrested hasn’t been found guilty yet, and meanwhile DNA evidence has been implicated in a number of wrongful accusations. One homeless California man had his DNA accidentally carried to a crime scene by paramedics, while a New Orleans filmmaker simply wasn’t the murderous cousin in his family’s tree.

That’s the most basic thing about DNA – you share it with your relatives. And black, Latino and other racialized families have plenty of bad history with doctors and police wielding new technology, from being made the unwitting subjects of experiments, to having planted evidence used to frame them.

This history is why the 100 black and brown workers of Bayham, Ont., are justified in feeling abused. It’s also why fears that the U.S. government’s grab at migrants’ most intimate data for further surveillance are unfortunately justified, too.

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Genetic science has the possibility to lead to spectacular breakthroughs, but we’ve all become too reckless in flinging away our privacy. Those who freely decide to spit into a 23andMe tube have the right to do so – and those who can’t or won’t give away their DNA have rights, too.

Editor’s note: This column has been updated to reflect the announcement on July 5 that U.S. officials are using DNA testing of migrant children in order to reunite separated families at the U.S.-Mexico border