Why do we need to distinguish ‘valid’ and ‘informed’ consent to medical treatment?

By Emma Cave.

Common law and ethics require that consent is voluntary, that it is made by a person with capacity and that it is sufficiently informed. But it does not follow that consent that is insufficiently informed will necessarily be considered in law to be invalid.

Since Montgomery in 2015, the requirement of informed consent is ‘firmly part of English law’. But the informational component for valid consent is merely that basic information is given to the patient. So if the consenting patient has capacity and makes a voluntary decision on the basis of basic information, their consent can be valid even if the law of negligence would deem it insufficiently informed.

One might ask: given that the law requires that consent is both valid and informed, why distinguish between the two? Several reasons are supplied in our recent article. The principal reason is that a failure to obtain valid consent can result in criminal assault and a civil claim of trespass to the person (battery) whereas a failure to obtain informed consent can constitute negligence. The differences in the operation of the two torts can have important practical ramifications:

The right not to know

The Supreme Court made clear in Montgomery that if a patient doesn’t want to know about all the material risks of a proposed treatment, it is within their right to refuse the information. But if they refuse any information, such as the fact that their right arm will be operated upon, their consent is unlikely to be valid.

If fuller information was required in order for the patient to give valid consent, then patients would be required to listen to it. They would lose an aspect of their right not to know.

The therapeutic exception

The ‘therapeutic exception’ is an exception to the rule that patients must be informed of all the material risks involved in treatment. It allows information to be withheld if it will cause the patient serious harm.

But if the therapeutic exception extended to even basic information then the patient would not need to be told anything about what treatment was planned. In law, this level of paternalism would not be considered justifiable.

Mental capacity

The courts have made clear that provided patients with borderline mental capacity can understand the ‘salient details’ they can make a valid decision. If capacity is assessed on the basis of an ability to provide valid consent, then their inability to understand more complex material risks will not necessarily indicate a lack of capacity.

But if consent is not considered valid unless the patient can grasp the intricacies of the material risks, reasonable alternatives and variants, then the effect could be to raise the threshold of capacity.


There are good reasons to distinguish between valid and informed consent. The GMC’s recent guidance on Decision Making and Consent, published since my article was released, refers very accurately to the requirement to ‘have the patient’s consent or other valid authority’ but doesn’t clearly separate this requirement from the need to ensure that decisions are informed. In my article I give several examples of professional guidance merging the two requirements.

And yet, if the distinction is misunderstood it could lead to misinterpretation that fails to uphod patient rights.


Paper title: Valid consent to Medical Treatment

Author: Emma Cave

Affiliations: Durham Law School, Durham University

Competing interests: None

Social media accounts of post author(s): Twitter: @profEmmaCave


(Visited 4,879 times, 1 visits today)