Last week, at a police convention in the US, a Florida police officer revealed he had obtained a warrant to search the GEDmatch database of a million genetic profiles uploaded by users of the genealogy research site. Legal experts said this appeared to be the first time an American judge had approved such a warrant.

“That’s a huge game-changer,” observed Erin Murphy, a law professor at New York University. “The company made a decision to keep law enforcement out and that’s been overridden by a court. It’s a signal that no genetic information can be safe.”

At the end of the cop’s talk, he was approached by many officers from other jurisdictions asking for a copy of the successful warrant.

Apart from medical records, your DNA profile is the most sensitive and personal data imaginable. In some ways, it’s more revealing, because it can reveal secrets you don’t know you’re keeping, such as siblings (and sometimes parents) of whom you were unaware. It can also contain information about inherited vulnerabilities that might be of great interest to, say, insurance companies. And, of course, your genetic profile contains information about your ethnic antecedents.

As these things go, the GEDmatch database is small. It’s dwarfed by the data troves of companies such as 23andMe, which has 10 million users and Ancestry.com, with 15 million. The scale of these databases means they could be used to identify a DNA profile even through distant family relationships. A 2018 study based on analysis of 1.28 million individuals in the databases and published in Science reported that “about 60% of the searches for individuals of European descent will result in a third cousin or closer match, which theoretically allows their identification using demographic identifiers”. The report predicted that “the technique could implicate nearly any US individual of European descent in the near future”.

At the moment, police forces are likely to have difficulty getting access to the vast databases of 23andMe and Ancestry.com, because people whose profiles are stored there didn’t know they might be used for law enforcement and couldn’t therefore have given their consent. But it turns out that GEDmatch had warned its users that their DNA could be used for “non-genealogical uses”. This, presumably, was what enabled Californian police to use it last year to identify and arrest a man suspected of more than 50 rapes and 12 murders in the 1970s.

Using DNA to solve such “cold” cases makes for great copy and is softening up public opinion for more extensive access to DNA databases for law enforcement. In that sense, it’s analogous to the campaign by the FBI and police forces everywhere for “back doors” to be engineered into encrypted messaging services. After all, so the reassuring argument goes, these special powers would require officials to get warrants from a judge under oversight from an independent commissioner (as, for example, in the UK Investigatory Powers Act). What could go wrong? Surely fighting crime strategically is always in the public interest?

Well, our experience over the past two decades should make us less complacent about the durability of democratic safeguards and norms. One thinks, for example, of the wholesale (and warrantless) mass surveillance undertaken by US government agencies in the wake of 9/11, practices that were supposedly overseen by a secret court and in some cases subsequently found to be unlawful. And we only found out about some of them by accident when Edward Snowden broke cover in 2013.

Years ago, an earlier National Security Agency whistleblower, who had built some of the NSA’s most effective surveillance tools, observed that the agency’s technology could put the US “a keystroke away from totalitarianism”. After the Snowden revelations, I put this to a very distinguished British politician who had held some of the highest offices of state. He looked at me with a pitying smile. Did I not realise that the UK and the US were democracies? he asked. The likelihood that a politician using such tools would rise to high office were zero. Three years after that conversation, Donald Trump was elected president. Six years later, Boris Johnson became prime minister and appointed as his strategic adviser a fanatical technocrat with apparently only a passing acquaintance with the rule of law.

And the moral of all this? It’s the old story with technology. On the one hand, as Iceland’s extensive research programme on genomics has shown, DNA databases have enormous potential for good, in terms of identifying genetic patterns in disease, devising preventive and curative strategies, understanding human evolution and so on. On the other hand, the data these databases contain is so sensitive that access to it has to be rigorously controlled and protected. And politicians – and their advisers – should never be allowed near them.

Just as I finished that sentence, a story from Reuters flashed on to my screen: the Trump administration is proposing to take DNA samples from immigrants detained by US authorities. Truly, in some areas, only the paranoid survive.

What I’m reading

Nature nurtured

Ten of the most important papers to appear in Nature make a fascinating list. They include studies of monoclonal antibodies, the structure of DNA, the first exoplanet and the discovery of the Antarctic ozone hole.

Character forming

A sobering analysis by the New York Times on how Trump reshaped the presidency in 11,000 tweets. Amazing what one can do with 140 characters.

Higher, further, faster

Rock climbing and the economics of innovation is an intriguing post on softmachines.org about, among other things, the importance of rubber.