Donna Dickenson writes: It’s 1946. On one side of the Atlantic, American lawyers are prosecuting Nazi doctors at Nuremberg for crimes against humanity – so-called “research” carried out on concentration camp prisoners. On the other side of the Atlantic, in Guatemala, the United States Public Health Service (PHS) is deliberately infecting prisoners and mental patients with syphilis in another “experiment” aimed at replacing the ineffective drugs used by soldiers during the war that had just ended.

It sounds too perverse to be true. Yet a special commission appointed by President Barack Obama has just confirmed that the Guatemalan experiments really did take place. Obama has also issued an apology to the people of Guatemala. But why did it take so long to get to this point?

Sixty-three years after the Guatemalan experiments, an American historian, Susan Reverby, was rummaging through archived medical papers from the 1940s. Reverby was completing a final task in her two decades of studying the PHS’s detestable Tuskegee experiments, in which hundreds of African-American men with late-stage syphilis were observed but not treated, even after penicillin was developed. She was examining the papers of Thomas Parran, US surgeon-general from 1936-1948, when the Tuskegee research was already in full swing. So, too, she found, was the previously unknown Guatemalan experiment.

For years, Tuskegee has been a byword for ethical abuses in scientific research – to the extent that President Bill Clinton apologised to its surviving “subjects”. Hard as it may be to believe, as Reverby was to discover, the abuse in Guatemala was even more egregious.