Leo Stanley, the chief physician of the San Quentin prison, was convinced that the offenders had a low testosterone level. So he started transplanting pig, deer and goat testicles. Nobody stopped him. He died old, respected and covered with honors.

(Staff: USA / Science & Ethics)

In 1913, an American doctor named Leo Stanley was appointed chief surgeon of the San Quentin prison in California. He was a respected man, with solid education, passionate about criminology and eager to understand why some people end up committing crimes. His theory was simple: criminals have less testosterone than ordinary people. And if the problem is hormonal, the solution could only be hormonal.

Thus began one of the most bizarre and least known medical experiments in the history of the United States. An experiment that lasted almost four decades, involved hundreds of inmates and caused almost no official reaction.

The theory that justified the horrors

Stanley believed that testosterone was the key to criminal behavior. If a man has too little testosterone, he becomes impulsive, frustrated, prone to violence. And if testosterone is given, it will calm down. The problem was that, at the time, testosterone could not be produced synthetically. The only source available was the animal glands.

In the absence of human donors, Stanley turned to pigs, deer and goats. He began to replace the inmates’ testicles with the animals, hoping that they would produce hormones and correct the behavior. There was no rigorous scientific protocol, there were no preliminary studies on animals, there was no informed consent. There were only inmates, a prison and a doctor convinced that he was right.

Experiments: from pig to human

The procedures were done in prison, with rudimentary tools and without adequate anesthesia. The prisoners were selected on obscure criteria, and some of them did not even understand what was happening to them. Stanley notes the results, notices changes in behavior, but has never published conclusive studies. Despite repeated failures, he continued.

Between 1913 and 1951, when he retired, Stanley performed hundreds of such transplants. It is not known exactly how many inmates died from infections, rejection or complications. It is not even known how many have survived with permanent sequelae. The files are incomplete, and the witnesses have long since disappeared.

One protest, no trial

In 1928, the family of a deceased detainee filed a complaint. The tribunal quickly closed it, with no consequence for Stanley. Otherwise, silence. No one asked if the experiments were ethical. No one has checked whether the results justify the suffering. No one defended the rights of people considered, at the time, less than citizens.

Stanley continued to be respected by the medical community. He published articles, held conferences, was considered a pioneer of forensic endocrinology. He died in 1976, at the age of 90, praised for his career. No one judged him for what he had done.

Echoes of an Ethics Without Ethics

The Stanley case is not unique. At the same time, in Nazi Germany, doctors were conducting similar experiments on camp inmates. In the United States, the Tuskegee experiment left hundreds of black men untreated for syphilis to study the evolution of the disease. In Guatemala, healthy people were deliberately infected with sexually transmitted diseases. All these cases eventually led to medical codes of medical ethics and the obligation of informed consent.

But Stanley escaped. He escaped because the prisoners had no lawyers, because the press was not interested, because the state did not see victims in them, but only criminals. He escaped because, in that era, science was considered a supreme authority, and doctors, priests of a secular religion.

Conclusion

Leo Stanley’s story is a tough lesson on what happens when science is left without ethical rein. It’s not just about a crazy doctor, it’s about a whole system that has closed its eyes. About a society that preferred to believe in progress at any cost, ignoring the suffering of those considered “less important”. Today, such experiments would be unthinkable. Or at least that’s what we like to think. But the question remains: how many other similar cases lie in the archives, waiting to be discovered?