Ethical, professional, federal, and campus guidelines for human subject research all require voluntary participation of subjects. The Nuremberg Code, developed by the International Military Tribunal that tried Nazi physicians for the "experiments" they performed on non-consenting inmates of concentration camps, was the first widely recognized document to deal explicitly with the issue of voluntary and informed consent. The first principle of the code states:

The voluntary consent of the human subject is absolutely essential. This means that the person involved should:

  • have legal capacity to give consent;
  • be so situated as to be able to exercise free power of choice, without the intervention of any element of force, fraud, deceit, duress, over-reaching, or other ulterior form of constraint or coercion; and
  • have sufficient knowledge and comprehension of the elements of the subject matter involved as to enable him to make an understanding and enlightened decision.

This latter element requires that before the acceptance of an affirmative decision by the experimental subject there should be made known to him the:

  • nature, duration, and purpose of the experiment;
  • method and means by which it is to be conducted;
  • all inconveniences and hazards reasonable to be expected; and
  • effects upon his health or person which may possibly come from his participation in the experiment.

The duty and responsibility for ascertaining the quality of the consent rests upon each individual who initiates, directs or engages in the experiment. It is a personal duty and responsibility which may not be delegated to another with impunity.

Therefore, each subject must give her or his agreement to participate in the research based upon adequate knowledge and understanding of relevant information, under circumstances that minimize the possibilities of coercion or undue influence.

Information about the research or what they should expect if they participate should not be withheld, especially if withholding it would influence a reasonable person's decision to participate or would damage his or her subsequent self-esteem. Information about risks shall never be withheld for the purpose of eliciting cooperation, and truthful answers should always be given to questions about the research. Certain groups, such as the economically disadvantaged, the very sick, and the institutionalized, may have compromised autonomy and should be protected against danger of being involved in research solely for administrative convenience or because they can be relatively easily manipulated. No coercion, explicit or implicit, should be used to obtain or maintain cooperation. Subjects must feel completely free to decline to participate and to withdraw their participation at any time. As established by the National Commission for the Protection of Human Subjects and documented in the Belmont Report:

  • An agreement to participate in research constitutes a valid consent only if voluntarily given.
  • This element of informed consent requires conditions free of coercion and undue influence.
    • Coercion occurs when an overt threat of harm is intentionally presented by one person to another in order to obtain compliance.
    • Undue influence occurs through an offer of an excessive, unwarranted, inappropriate or improper reward or other overture in order to obtain compliance.
    • Also, inducements that would ordinarily be acceptable may become undue influences if the subject is especially vulnerable.

Unjustifiable pressures usually occur when persons in positions of authority or commanding influence -- especially where possible sanctions are involved -- urge a course of action for a subject. A continuum of such influencing factors exists, however, and it is impossible to state precisely where justifiable persuasion ends and undue influence begins. But undue influence would include actions such as manipulating a person's choice through the controlling influence of a close relative and threatening to withdraw health services to which an individual would otherwise be entitled.