Electron micrograph of the Treponema pallidum bacterium At least 83 Guatemalans are thought to have died not long after being deliberately infected with syphilis and gonorrhoea in the 1940s, a presidential commission in Washington has heard. US government scientists infected hundreds of Guatemalan prisoners, psychiatric patients and sex workers to study the effects of penicillin.
None of those infected consented.
Guatemala's vice-president said an apology would be made to the people, as local doctors were also involved.
The head of the commission, Amy Gutmann, called the research a "shameful piece of medical history".
The Presidential Commission for the study of Bioethical Issues said some 5,500 Guatemalans were involved in all the research that took place between 1946 and 1948.
Of these, some 1,300 were deliberately infected with syphilis, gonorrhoea or another sexually transmitted disease, chancroid.
And of that group only approximately 700 received some sort of treatment.
According to documents the commission had studied, at least 83 of the 5,500 subjects had died by the end of 1953.
'Grievously wrong'
The body was unable to say how many - if any - of those deaths were caused directly or indirectly by the deliberate infections.
But Dr Gutmann lambasted those responsible for the research.
"Those involved in the study failed to show a minimal respect for human rights and morality in the conduct of research," she declared, in her concluding remarks to the panel.
Many of the actions were "grievously wrong", she added, and those individuals behind the study were "morally culpable to various degrees".
"Civilisations can be judged by the way they treat their most vulnerable," Dr Gutmann said, before stressing that "we failed to keep that covenant".
President Obama set up the commission when the research first came to light last year.
He also apologised to his Guatemalan counterpart, Alvaro Colom, saying the acts ran contrary to American values.
Earlier this year, a group of Guatemalans who were infected and their relatives announced that they were suing the US government over the affair.
The commission is due to publish its first report, to establish the historical facts, next month.
Its final report, in December, will examine the ethical issues involved, and aims to "make sure this never happens again".