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Turi King
UK, Doubleday; US, Transworld Digital

In 1993, a 62-year-old woman in the town of Idar-Oberstein in Germany was found strangled with florist wire. DNA found on a coffee cup suggested that two people were present besides the victim and that one of the apparent killers was a woman.

In 2001, the suspected female murderer’s DNA turned up again in Germany, this time on the body of a strangled 61-year-old man in Freiburg. Then her DNA started appearing at crime scenes in France and Austria, too.

In 2007, the mysterious woman hit the headlines when two police officers were shot – one fatally – in their car in the German city of Heilbronn, and her DNA was found in the back seat. These killings sparked a major hunt for “the Phantom of Heilbronn”, as she became known.

But the Phantom proved elusive, despite being linked to 41 crimes via her DNA. In some cases, her accomplices were caught, but they denied that any woman was involved. Police started to consider the possibility that the phantom was transgender. It wasn’t until 2009 that the Phantom was finally identified – as a woman who worked in a factory that made swabs for DNA testing. The Phantom of Heilbronn really was a phantom – police had wasted years chasing a non-existent killer.

“There are definitely instances when DNA is not the silver bullet people think it is,” writes Turi King in The Secrets of Our DNA: How genetics has changed the world.

King studied archaeology initially, but switched to genetics after being enthralled by a lecture describing how DNA was used to show that a man who drowned in Brazil in 1979 was, in fact, Josef Mengele, the Nazi doctor known as the Angel of Death.

“What has always hooked me about DNA has been the stories, the cases where the DNA was the key to answer a question, solve a mystery, help someone answer a long-held family mystery, provide information as to their propensity for genetic disease, exonerate someone, help convict someone, or help someone find part of their identity by tracing a hitherto unknown parent,” writes King.

Her book is full of such tales – including the story of how Richard III of England, killed in battle in 1485, was found under a car park in Leicester. King led the study of the DNA of the skeleton that turned out to be his, propelling her to fame.

As she describes, we all shed DNA all the time, and it can end up in surprising places. “You’re almost certainly carrying around DNA from loved ones, and even your work colleagues, whether you want to or not.” This means that finding someone’s DNA at a crime scene doesn’t mean they are guilty of the crime, as the case of the Phantom of Heilbronn showed. But there is a tendency to believe that it does.

Take the case of Amanda Knox, a flatmate of Meredith Kercher, murdered in Italy in 2007. There was abundant evidence against a man called Rudy Guede, but Knox and her boyfriend Raffaele Sollecito were also convicted on the basis of dubious DNA evidence.

For instance, Sollecito’s DNA was on a bra clasp found on the floor of Kercher’s room 41 days after the murder. Yet videos showed that the clasp had been passed around by police wearing gloves with which they had handled other items in the flat. In fact, during a later appeal, experts identified 53 occasions during which procedures to prevent contamination weren’t followed. Because Sollecito’s DNA was undoubtedly present on various items in the flat, it is quite likely that the police themselves transferred it to the clasp.

Knox and Sollecito spent about four years in prison before their convictions were overturned. “The case starkly demonstrates the double-edged sword of modern forensic DNA capabilities,” King writes. “While minute traces of DNA can now be detected with astonishing sensitivity… this brings with it the possibility of misinterpretation of what those results mean.”

The fact that DNA testing has limits as well as remarkable power is one of the themes running through this book. Take the case of US Senator Elizabeth Warren, whose claim to have Indigenous American ancestry was confirmed by DNA testing.

Yet as King explains, a person could well have an ancestor from a particular group without having any of their DNA. We only inherit a random half of our parents’ DNA, and the lost half can include any remaining DNA from more distant ancestors. “Even if Warren’s DNA test had come back as negative… that wouldn’t mean that the family story wasn’t true,” King writes.

Then we come to the analysis of Adolf Hitler’s genome, led by King for the 2025 TV documentary Hitler’s DNA: Blueprint of a dictator. I was highly critical when I reviewed this documentary because it implied that Hitler’s DNA predestined him to do what he did, that is, that genetics determines our fate. I also pointed out that Hitler didn’t act alone.

What does King say in the chapter discussing Hitler’s genome? “Genetic determinism has been discredited… DNA cannot tell us about the decisions that someone will make in life” and “it’s important to stress that Hitler did not act alone”. King says she emphasised the limitations of DNA to the company that made the documentary and that “they took on board” these limitations.

In my view, they did not do so. Given the contrast between the documentary and the book, I can’t help but suspect that King wasn’t entirely happy with the end product, even if she won’t say so publicly.

Should you read this book? A lot of this lengthy volume consists of explanations of the science. Knowing most of it already (it’s my job), I found these sections a bit wearisome, but if you aren’t up to speed on the ins and outs of the double helix, you may appreciate this detail.

What will grip you, though, are King’s many DNA-related stories. There are plenty I knew nothing about, such as the case of the Phantom of Heilbronn. Even with those I had already heard about, such as Horsegate – the discovery in 2013 that many beef products in Europe contained horsemeat – King adds a lot of colour and insight. Well worth reading.

Three more great takes on genetics

written and directed by Andrew Niccol

This 1997 dystopian film (starring Ethan Hawke, above) explores the perils of a society that believes in genetic determinism. It is perhaps even more relevant today than when it was made.

created by Graeme Manson and John Fawcett

One way to think about genetic determinism is to ask: just how similar would clones be to each other? TV series Orphan Black (with Tatiana Maslany, above) is about a woman who finds that she is one of dozens of clones.

by Roxanne Khamsi

We tend to view our genome as fixed and unchanging, but that’s far from the truth: we are all mutating mutants. As this book reveals, there may be trillions of new mutations in your body every day.