Because of unpredictability and high possibility of abnormal results by clinical trials compared to general medical behaviors, a procedure for ensuring with sufficient explanations by investigators must be secured. Therefore, in a sequence of clinical trials, what kinds of scope, stage, and method of explanations provided by investigators, including doctors or researchers, to trial subjects are closely related to the compensation for damages by violation of liability for explanation. In case of application of clinical trials to patients who have critical illness such as cancer, issues of "Quality of Life" regarding trial subjects, cancer patients, should be discussed. Especially, in case of clinical trials for terminal cancer patients, the right of subjects' self-determination, which is a fundamental principle in medical behaviors, should be discussed. The right of self-determination includes participation in clinical trials for the possibility of life-sustaining even a little bit, or no participation in clinical trials in order to have a time for completing the rest of his life. Like this, if the extent and scope of explanations related to the issues of "Quality of Life" are raised as main issues, the evaluation of "Quality of Life", should be a prerequisite. In many occasions, realistically, despite bad results such as deaths or serious adverse drug reactions after clinical trials, it may not be easy for compensating to trial subjects or their survivors, who requested civil compensation for damage. Futhermore, in abnormal results after concealment of clinical trials or performance of clinical trials without permission, and in the case of trial subjects' failures of proving proximate cause between the clinical trials and abnormal results, problematic results such as no protection to the trial subjects could be occurred. In performing clinical trials, investigators should provide sufficient explanations for trial subjects and secure voluntary informed consents from the trial subjects. Therefore, clinical trials without trial subjects' permissions and the informed consent process violate trial subjects' rights of self-determination, and the investigators shall be liable for compensation for damages. Then, issues might be addressed are what are essential contents of patients' "rights of self-determination" infringed by clinical trials without subjects' permissions. Two perspectives about patients' rights of self-determination might be considered. One perspective regards physical distress of patients (subjects) from therapies without sufficient explanations as the crux of the matter. The other perspective regards infringement of human dignity caused by being subjects without permission as the crux of the matter irrespective of risks' big and small influences. This research follows perspective of the latter. Forming constant fiduciary relation between investigators (doctors) and subjects (patients) pursuant medical contracts, and in accordance with this fiduciary relation, subjects, who are patients, have expectations of explanations and treatments by the best ways. If doctors and patients set this forth as a premise, doctors should assume civil liability when doctors infringe patients' expectations.