Oral consent should be considered when obtaining explicit, active consent is essential, but the risk or discomfort involved in the process is too great to make written consent a valid option. Some populations, such as criminals, undocumented immigrants, or the homeless, may be placed at legal risk, or be suspicious of leaving a written trace, and refuse to participate. Or, the topic of the research may be highly sensitive, because it concerns behavior and attitudes that, even though legal, are socially condemned. Should the records be exposed, or a criminal investigation take place, researchers themselves may become liable. Oral consent is also a valid option for participants that are uncomfortable reading and writing, and may be too embarrassed by the written consent process to participate in research. In that case, the researcher should record the reading of a consent statement, and the clear answers of the participants indicating willingness to participate. The recording verifies informed oral consent.
Separate consent forms have been designed to provide explicit, active written consent for photo, audio, and video recording. Capturing someone’s image is more invasive than other forms of research. By signing the photo, audio, video consent form,participants indicate that they are fully aware of the type of data that will be collected.
Explicit consent. Participants give consent by answering a specific question about their willingness to participate. This may be done in written (consent form) or oral form.
Written consent. Participants give their consent by filling out a consent form. Written consent guarantees active and explicit consent, thus offering the highest guarantees to the participant. It is most appropriate in studies that contain some level of risk, but also in many studies with no risk above those of daily life, when participants disclose personal or sensitive information, when they are exposed to deception, or any experimental treatment. Experiments and in-depth interviews in particular should consider written consent.