- subjects who are known or suspected: not to comply with the study directives or meet the required visit schedules; not to be reliable or trustworthy; not to be capable of understanding and evaluating the information given to them as part of the formal information policy (informed consent), in particular regarding the risks and discomfort to which they would agree to be exposed; to be in such a precarious financial situation that they no longer weigh up the possible risks of their participation and the unpleasantness they may be involved in.