The Nuremberg Code is a set of ten ethical principles governing human experimentation, created in 1947 as part of a U.S. military tribunal’s verdict against Nazi doctors who performed brutal medical experiments on concentration camp prisoners. It was the first major international document to establish that no experiment should ever be conducted on a person without their voluntary, informed consent. Though not a legally binding treaty, the code became the foundation for virtually every research ethics framework that followed.
Why the Code Was Written
The Nuremberg Code emerged directly from what is known as the Doctors’ Trial, officially titled U.S.A. vs. Karl Brandt, et al. The indictment was filed on October 25, 1946, and the tribunal delivered its judgment on August 19, 1947. Twenty-three German doctors and administrators stood accused of organizing and participating in war crimes and crimes against humanity through medical experiments and procedures inflicted on prisoners and civilians.
The experiments that prompted the trial were staggering in their cruelty. At Auschwitz, Josef Mengele conducted genetic research on living people, especially twins, correlating data from examinations of living prisoners with analyses performed after they were killed. His investigations included questions about inherited traits like eye color and the genetics of proteins involved in infection resistance. At Dachau and Ravensbrück, SS physicians organized trials of antibiotic and homeopathic treatments by deliberately infecting healthy prisoners. They injected people with material from the festering wounds of other inmates and, in some cases, placed pieces of wood and glass into open wounds to simulate war injuries more realistically. Some victims received experimental treatments while others received no therapy at all.
These were not rogue acts by a handful of individuals. The experiments were systematic, organized through official channels, and carried out by trained physicians who understood exactly what they were doing. When the tribunal convicted the defendants, the judges recognized that existing medical ethics offered no clear, codified standard to point to. So they wrote one.
The Ten Principles
The code’s first principle is its most famous, and it opens with an unambiguous declaration: “The voluntary consent of the human subject is absolutely essential.” That word “absolutely” was deliberate. The judges left no room for exceptions, no circumstances under which an experiment could proceed without a person’s free and informed agreement. The remaining nine principles address the broader conditions under which human experimentation can be considered ethical.
- Voluntary consent. The person must be able to exercise free choice, must understand what the experiment involves, and must not be subjected to force, fraud, deceit, or coercion of any kind.
- Necessary purpose. The experiment must aim to produce results that benefit society and that cannot be obtained by any other method.
- Prior groundwork. The experiment should be based on results from animal studies and existing knowledge of the disease or problem, so that the expected outcomes justify performing the experiment.
- Avoidance of unnecessary harm. The experiment must be designed to avoid all unnecessary physical and mental suffering and injury.
- No expectation of death or disabling injury. No experiment should be conducted if there is reason to believe it will cause death or disabling injury, with a possible exception when the experimenting physicians also serve as subjects.
- Risk proportional to benefit. The degree of risk must never exceed the humanitarian importance of the problem the experiment is designed to solve.
- Proper preparation and facilities. Adequate preparations must be made and proper facilities provided to protect the subject against even remote possibilities of harm.
- Qualified experimenters. Only scientifically qualified persons should conduct the experiment, exercising the highest degree of skill and care throughout.
- Right to withdraw. The subject must be free to end the experiment at any point if they feel they have reached a physical or mental state where continuation seems impossible.
- Experimenter’s duty to stop. The scientist in charge must be prepared to terminate the experiment at any stage if they have reason to believe that continuation is likely to result in injury, disability, or death.
Several of these principles place responsibility on the researcher, not just the participant. The code doesn’t simply say people can opt out. It requires the scientist to actively monitor for danger and to shut down the experiment before harm occurs, even if the participant hasn’t complained.
What the Code Changed
Before 1947, medical ethics around experimentation were largely informal. Physicians operated under broad professional norms like “do no harm,” but there was no widely recognized standard specifying what researchers owed to their human subjects. The Nuremberg Code introduced the idea that consent alone wasn’t enough. The entire structure of an experiment, from its scientific justification to the qualifications of the people running it to the physical safeguards in place, had to meet ethical standards before a single participant could be enrolled.
The concept of informed consent, in particular, was transformative. The code didn’t just require that a person say yes. It required that the person fully understand the nature, duration, and purpose of the experiment, the methods involved, the potential hazards, and the possible effects on their health. This was a far more demanding standard than anything that existed in medical practice at the time.
Its Role in Modern Research Ethics
The Nuremberg Code is not a law or a binding international treaty. It was part of a judicial ruling in a specific criminal case. No government formally ratified it the way nations ratify treaties. Yet its influence has been enormous. The U.S. Department of Health and Human Services describes the code as “the prototype of many later codes intended to assure that research involving human subjects would be carried out in an ethical manner.”
The most direct descendant is the Declaration of Helsinki, first adopted by the World Medical Association in 1964. Helsinki expanded on the Nuremberg principles, adding requirements like independent ethics committee review of research protocols and special protections for vulnerable populations. It has been revised multiple times since then. The most recent revision, completed in 2024, addresses modern challenges including the role of artificial intelligence in health research, ethical data governance, and the need for global inclusivity. Notably, the 2024 update changed the language from research “subjects” to “participants,” a shift that reflects how profoundly the relationship between researchers and the people they study has evolved since 1947.
In the United States, the Belmont Report of 1979 drew a direct line from the Nuremberg Code to American research regulations. The Belmont Report established three core principles (respect for persons, beneficence, and justice) that still govern federally funded research today. Every institutional review board that approves a clinical trial in the U.S. operates under rules that trace back, through the Belmont Report and the Declaration of Helsinki, to the ten principles written in a Nuremberg courtroom.
Why It Still Matters
The Nuremberg Code was written in response to extreme, wartime atrocities. But the ethical failures it addressed have not been limited to Nazi Germany. In the decades after the code was published, researchers in the United States conducted the Tuskegee syphilis study, in which hundreds of Black men with syphilis were deliberately left untreated so scientists could observe the disease’s progression. That study ran from 1932 to 1972, well after the Nuremberg principles were established. It was one of the scandals that directly prompted the Belmont Report.
The code’s enduring relevance lies in its simplicity. Its principles are not tied to a specific technology, disease, or era. The idea that people must freely choose to participate in research, that they must understand what they’re agreeing to, that they can leave at any time, and that scientists bear responsibility for their safety applies just as cleanly to a modern gene therapy trial or an AI-driven diagnostic study as it did to the experiments it was written to condemn.