Consent is often mistakenly used as shorthand to describe when a person completes and signs a consent form. In fact, consent has many components and is more properly viewed as a process. It covers a whole spectrum of interactions that may be more or less invasive or harmful and require varying amounts of communication between the parties.
Where the risk of harm is small the law can recognise imputed consent, where consent is assumed based on what is known about people. For example, because people want good quality medical treatment, it is assumed that people will not mind their x-rays, with any personal identifiers removed, being used to train doctors.
Implied consent can be presumed based on a person’s actions. If a person rolls up their sleeve when a nurse suggests taking their blood pressure, the nurse can assume that the person has consented to have it taken. Informed (or express or explicit) consent is more specific in the requirements it makes for both parties. It usually requires more information to be given to the person making the decision and requires that they make a specific choice, either yes or no, because the harm they might suffer is greater than in the other cases. For example, a researcher must obtain your consent before entering you into a clinical trial to test a new medicine, or a doctor before performing an invasive treatment. The greater the potential for harm, the greater need there is for informed consent.
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