The Nuremberg Code is a set of ten ethical principles governing human experimentation, issued in August 1947 as part of the verdict in the trial of Nazi doctors who had conducted lethal experiments on concentration camp prisoners. Its most famous and foundational rule is that the voluntary consent of a human research subject is “absolutely essential.” Though it was not drafted as a statute or treaty, the Code became the first major international document to lay down explicit ethical boundaries for medical research, and every subsequent framework for protecting research subjects traces its lineage back to it.
How the Code Came About
After World War II, twenty-three Nazi physicians and administrators were charged with murder and torture for conducting experiments on concentration camp prisoners. The proceedings, formally known as United States of America v. Karl Brandt et al., are commonly called the Doctors’ Trial. The experiments involved exposing prisoners to freezing temperatures, low atmospheric pressures, infectious diseases, and mustard gas, among other horrors, often with fatal results. The defendants were tried before an American military tribunal at Nuremberg between December 1946 and August 1947.
Three physicians played central roles on the prosecution side. Two were American: Leo Alexander, a psychiatrist and neurologist who served as a medical consultant to the prosecution, and Andrew C. Ivy, a physiologist who testified as an expert witness. The third, Werner Leibbrandt, was a German medical historian.1PubMed Central. American Doctors at the Nuremberg Medical Trial Alexander drafted a memorandum outlining six points he considered necessary for ethically permissible human experimentation and submitted it to the prosecution team during the trial. Scholarly analysis suggests that this memo served as the blueprint for what became the ten-point Nuremberg Code, though the final version was likely shaped by collaboration among the prosecutors and the judges themselves.2PubMed. Leo Alexander’s Blueprint of the Nuremberg Code
The judges included the Code as part of their written judgment, not as a standalone legal instrument. This detail matters: the Code was embedded in a court ruling rather than enacted as legislation or adopted by a governing body. It had enormous moral authority but no built-in enforcement mechanism outside the trial that produced it.
What the Ten Principles Actually Say
The Code’s ten principles cover three broad areas: the rights of research subjects, the qualifications and responsibilities of researchers, and the design of experiments themselves. But the weight is not evenly distributed. The first principle, on voluntary consent, dwarfs the other nine. While each of the remaining principles is expressed in a single sentence, the consent principle is followed by two detailed explanatory paragraphs spelling out what “voluntary consent” means in practice.3PubMed Central. Beyond Nazi War Crimes Experiments: The Voluntary Consent Requirement of the Nuremberg Code at 70
The language of that first principle is striking for how comprehensively it tries to close loopholes. The subject must have “legal capacity to give consent,” must be “so situated as to be able to exercise free power of choice, without the intervention of any element of force, fraud, deceit, duress, overreaching, or other ulterior form of constraint or coercion,” and must have “sufficient knowledge and comprehension of the elements of the subject matter involved as to enable him to make an understanding and enlightened decision.”4PubMed Central. Beyond Nazi War Crimes Experiments: The Voluntary Consent Requirement of the Nuremberg Code at 70 In other words, mere agreement is not enough. The person has to understand what they are agreeing to, and the agreement must be genuinely free.
The remaining nine principles address other ethical requirements. Among them:
- Scientific justification: The experiment must aim to produce results that benefit society and cannot be obtained by other means.
- Prior animal testing: Experiments on humans should be preceded by results from animal experimentation that justify expecting the procedure to be safe and productive.
- Avoidance of unnecessary harm: All unnecessary physical and mental suffering must be avoided.
- Proportional risk: The degree of risk must never exceed what the humanitarian importance of the problem to be solved would justify.
- Qualified researchers: Only scientifically qualified persons should conduct the experiments.
- Right to withdraw: The human subject must be free to end the experiment at any time if they reach a state where continuing seems impossible to them.
- Researcher’s duty to stop: The researcher must be prepared to terminate the experiment at any stage if they have reason to believe it will result in injury, disability, or death.
The Code positioned voluntary consent as the foundation on which everything else rested. This emphasis on the individual’s autonomy was a direct response to what had happened in the camps, where prisoners had no choice at all.
The Code Did Not Come from Nowhere
One common assumption is that there were no rules governing human experimentation before Nuremberg. That is not quite right. Germany itself had binding regulations on the topic dating back to 1931. Known as the Reichsrundschreiben (Reich Circular), these guidelines were issued by the German Interior Ministry and remained technically in force throughout the Third Reich.5PubMed Central. The Nuremberg Code-A critique The 1931 guidelines required informed consent and imposed restrictions on research with vulnerable populations. In some respects, they were stricter than the Nuremberg Code that followed.6Oxford Academic. Reichsrundschreiben 1931: pre-Nuremberg German regulations concerning new therapy and human experimentation
The defendants at the Doctors’ Trial actually tried to have their conduct judged by the 1931 guidelines, which they argued were the relevant standard. The prosecutors rejected this approach and instead tried them for crimes against humanity. The judges ultimately included the Nuremberg Code in their judgment, and six of its ten principles can be traced back to the 1931 regulations. Two of the four newly inserted principles have been criticized as open to misinterpretation.7PubMed Central. The Nuremberg Code-A critique
The existence of the 1931 guidelines makes the Nazi experiments even more damning: the rules were already on the books in Germany. They were simply ignored. This pattern of having ethical standards on paper and ignoring them in practice would, disturbingly, repeat itself in the decades after Nuremberg.
Why the Code Was Ignored for Decades
The Nuremberg Code is often described as a watershed moment in research ethics, and in historical terms it was. But in practical terms, its impact on actual research conduct in the years immediately after 1947 was shockingly small. American researchers, in particular, treated it as something that applied to Nazi doctors, not to themselves.
The Advisory Committee on Human Radiation Experiments (ACHRE), established by the U.S. government to investigate Cold War-era radiation research on human subjects, examined what role the Nuremberg Code played in the norms and practices of American medical researchers. The committee’s conclusion was blunt: the Code, at the time it was issued, had little effect on mainstream medical researchers engaged in human subjects research.8PubMed. US medical researchers, the Nuremberg Doctors Trial, and the Nuremberg Code. A review of findings of the Advisory Committee on Human Radiation Experiments During the Cold War, U.S. government agencies sponsored experiments that exposed soldiers, prisoners, hospital patients, and others to radiation, often without their knowledge or consent. The Code was on the books, but the people running these programs either did not know about it, did not consider it relevant to their work, or chose to disregard it.
The most infamous example of post-Nuremberg ethical failure is the Tuskegee syphilis study, which ran from 1932 to 1972. U.S. Public Health Service researchers withheld treatment from Black men with syphilis in order to observe the disease’s progression, never informing the participants of their diagnosis or of the availability of penicillin. The study continued for twenty-five years after the Nuremberg Code was issued. Neither the Code, nor the Catholic Church’s position expressed by Pope Pius XII in 1952, nor the Declaration of Helsinki in 1964 deterred the Tuskegee researchers from continuing.9Actas Dermo-Sifiliográficas. Syphilis and Human Experimentation From World War II to the Present: A Historical Perspective and Reflections on Ethics
The pattern suggests that ethical codes without enforcement infrastructure are easy to set aside. The Nuremberg Code relied on moral authority. It had no oversight body, no reporting mechanism, and no institutional structure to hold researchers accountable. Those features would only emerge later, and only after more scandals forced the issue.
How the Code Shaped Everything That Followed
Despite its limited immediate impact, the Nuremberg Code became the foundation document for the modern framework of research ethics. Subsequent guidelines and regulations have built on its principles, refined them, and added the institutional machinery the Code lacked.
The World Medical Association adopted the Declaration of Helsinki in 1964, which expanded on the Code’s principles and addressed some of its gaps, particularly around research involving patients who cannot provide their own consent. The Declaration has been revised multiple times since, most recently in 2013.10PubMed Central. The ethics of global clinical trials In 1966, the American anesthesiologist Henry Beecher published a landmark paper documenting twenty-two examples of unethical research conducted by mainstream American scientists, many of which involved experiments on patients who had not consented. This paper helped shatter the comfortable notion that ethical abuses in research were exclusively a Nazi phenomenon.
The exposure of the Tuskegee study in 1972 triggered the most important regulatory response in the United States. Congress passed the National Research Act in 1974, which created the National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research. That commission produced the Belmont Report in 1979, which distilled research ethics into three core principles: respect for persons, beneficence, and justice.11PubMed Central. The creation of the Belmont Report and its effect on ethical principles: a historical study The Belmont Report, in turn, led to the federal regulations known as the Common Rule, which mandated Institutional Review Boards (IRBs) at every institution receiving federal research funding. These boards review proposed studies before they begin, assess risks, and ensure informed consent procedures are adequate.12PubMed Central. Ethical Guidelines and the Institutional Review Board – An Introduction
The lineage is clear. The Nuremberg Code set the standard, and every subsequent attempt to regulate human experimentation has built upon it.13PubMed Central. Beyond Nazi War Crimes Experiments: The Voluntary Consent Requirement of the Nuremberg Code at 70 Where the Code proclaimed principles, later frameworks added procedures, oversight committees, and legal consequences. The voluntary consent requirement that the Code placed first remains at the center of every modern research ethics framework.
Where the Code’s Strict Standards Create Tensions
The Nuremberg Code’s absolute requirement of voluntary consent was a strength in its original context. It was a definitive rejection of the idea that scientific progress could justify experimenting on people against their will. But taken literally, it creates problems that later ethics frameworks have had to work around.
The most obvious tension involves people who cannot consent for themselves: young children, people with severe cognitive disabilities, and patients who are unconscious. The Code does not address proxy consent at all. Read strictly, it would prohibit nearly all pediatric research and any study involving adults who lack the capacity to provide informed consent. The Declaration of Helsinki and subsequent regulations addressed this gap by allowing consent from legally authorized representatives under specific safeguards, but the Code itself offers no provision for it.
Emergency medicine presents another difficult case. If a person arrives at a hospital unconscious after a traumatic injury, they cannot consent to participate in a clinical trial testing a new resuscitation technique. Yet the only way to develop better emergency treatments is to test them in genuine emergencies. The U.S. Food and Drug Administration has established an Exception from Informed Consent policy specifically for emergency research, which mandates community consultation as a way of protecting patient autonomy when individual consent is impossible.14PubMed Central. Exception from informed consent for emergency research: consulting the trauma community This is a pragmatic workaround, but it represents a clear departure from the Code’s original absolutism.
Clinical trials in developing countries raise yet another set of concerns. The Code requires that consent be free from “any element of force, fraud, deceit, duress, overreaching, or other ulterior form of constraint or coercion.” But when participation in a clinical trial is the only way for someone to access medical treatment at all, the line between voluntary choice and economic coercion becomes blurry. The growth of international clinical trials, particularly in low-income countries, has forced ongoing debate about whether the Code’s principles are being honored in spirit when the structural conditions make refusal impractical.15PubMed Central. The ethics of global clinical trials
The Controversial Animal Testing Principle
Most discussions of the Nuremberg Code focus on informed consent, but Principle 3 has drawn its own critics. It states that human experiments should be based on prior results from animal experimentation. This requirement was intended as a safety measure: test on animals first, and only proceed to humans once there is reason to believe the procedure will not cause harm. The principle was subsequently incorporated into national and international laws governing drug development.
Some researchers have argued that this requirement is outdated and, paradoxically, may harm rather than protect human subjects. A critique published in BMC Medical Ethics contended that the animal testing requirement was based on scientifically outdated principles, was influenced by people with a vested interest in animal experimentation, serves no useful function in many modern contexts, increases the cost of drug development, and prevents otherwise safe and effective therapies from reaching patients.16PubMed Central. The Nuremberg Code subverts human health and safety by requiring animal modeling The argument rests on the observation that animal models frequently fail to predict human responses, meaning that drugs which pass animal tests may still harm humans, while drugs that fail in animals may have worked in people.
This is not a fringe debate. Advances in organ-on-a-chip technology, computer modeling, and human cell-based assays have given researchers tools that can, in some cases, predict human responses more accurately than animal models. The FDA Modernization Act 2.0, signed into U.S. law in 2022, formally removed the requirement that drugs must be tested on animals before human trials, allowing non-animal alternatives. The shift effectively sidesteps the Nuremberg Code’s third principle in a way that most ethicists see as consistent with the Code’s deeper intent: protecting human subjects from unnecessary harm.
The Right to Withdraw Meets Permanent Technology
Principle 9 of the Nuremberg Code states that a research subject “should be at liberty to bring the experiment to an end” at any point during the study. For conventional medical research, this is straightforward: you can stop taking an experimental drug, leave a trial, or decline further visits. But newer categories of experimental technology are testing the limits of what withdrawal actually means.
Brain-computer interfaces and xenotransplantation (transplanting animal organs into humans) both involve interventions that may be difficult or impossible to reverse. If a person receives a genetically modified pig kidney as part of a clinical trial, they cannot simply return it. Similarly, a participant in a brain-computer interface trial who has a device surgically implanted in their brain may face serious medical risks from having it removed. In both cases, the research institution may also need to monitor the participant for years or even for life to track long-term outcomes, creating tension with the subject’s right to walk away from the study entirely.17Medical Research Archives. Clinical Trials of Xenotransplantation and Brain-Computer Interfaces: Commonalities and Cautions in Ethics Policy
This is not an abstract concern. Several companies are already running or planning human trials of brain-computer interfaces. As these trials grow, the question of how to honor the right to withdraw when the experimental intervention is literally inside someone’s body will become a defining ethical challenge. The Nuremberg Code articulated the principle; the task now is figuring out what it means when the technology was unimaginable in 1947.
Human Challenge Trials and the Limits of Acceptable Risk
Human challenge trials, in which healthy volunteers are deliberately infected with a pathogen to test a vaccine or treatment, sit at an uncomfortable intersection of several Nuremberg principles. The Code requires that experiments avoid unnecessary suffering, that the risk be proportional to the humanitarian importance of the problem, and that consent be genuinely informed. Challenge trials meet the consent requirement head-on: participants knowingly agree to be made sick. But the acceptability of the risk depends heavily on the disease involved and on whether effective treatments exist if something goes wrong.
Interest in challenge trials surged during the early months of the COVID-19 pandemic, when thousands of volunteers offered to be deliberately infected with SARS-CoV-2 to speed vaccine development. Ethicists debated whether such trials could satisfy the Code’s requirement that the risk not exceed the humanitarian importance of the problem. The Nuremberg Code, researchers have argued, continues to offer valuable guidance for assessing the ethics of human challenge experiments, particularly regarding the acceptable limits of research risks and the social value of research needed to justify exposing participants to those risks.18PubMed Central. Human Infection Challenge Experiments: Then and Now The Code does not ban challenge trials outright, but its principles impose a demanding standard that each proposed study must clear.
When the Code Gets Invoked Incorrectly
The Nuremberg Code has been widely invoked in public debates where it does not technically apply, most visibly during disputes over vaccine mandates and public health measures during the COVID-19 pandemic. Protesters and social media posts frequently cited the Code as proof that mandatory vaccination is illegal, arguing that any medical intervention requires individual consent under Nuremberg’s first principle.
This argument misreads the Code in several ways. The Nuremberg Code governs experimental research, not routine medical care or established public health interventions. A vaccination program using a licensed, approved vaccine is not a medical experiment. The Code’s consent principle addresses participation in research studies, not the broader question of whether governments can require vaccinations as a condition of employment, school enrollment, or international travel. Those questions are governed by public health law, constitutional law, and regulatory authority, all of which have separate and well-established legal frameworks.
The misapplication also strips the Code of its historical context. It was written in response to experiments in which prisoners were frozen, infected, poisoned, and killed without any pretense of consent. Equating that context with a public vaccination campaign, however one feels about mandates, distorts the document’s purpose and minimizes the atrocities it was meant to address. Scholars have noted that this kind of misuse of the Code represents one of the more persistent bad arguments deployed against vaccination policies, conflating ethical principles specific to research with the entirely separate legal and ethical frameworks governing public health measures.