In an article for the Journal of Medical Ethics (abstract and article attached below), Professor Kenneth Boyd questions the possibility of participants in medical research ever giving truly informed consent. Boyd outlines various difficulties. The complex nature of much medical research may prevent the researcher from giving full details, particularly in the time available. The potential participant may be vulnerable or confused. The researcher may not be ethical. The participant may have a belief system which conflicts with the aims or methods of research.
While Boyd's individual points are all credible, the idea that they add up to the impossibility of informed consent appears to be a conflict between the practical problems of medicine and the abstract ideals of philosophy. Perfectly informed consent may be impossible. In one sense at least, it is axiomatically impossible, since even the researcher has no idea what all the ramifications of their research will be. The participant clearly cannot give consent to everything that might possibly happen in the future as a result of the research. However, a counsel of absolute perfection would preclude all research and, for that matter, all medical treatment. Boyd's objections are perhaps best regarded as a checklist for the researcher or supervising body to ensure that consent is as informed and voluntary as possible, and that the researcher behaves ethically.