In this case it was argued that the tribunal had addressed the s3 criteria for a patient who was detained under s2. (1) The Upper Tribunal decided that the First-tier Tribunal had not misdirected itself in this way. (2) However, the judge considered the criteria: he set out why he considered them different (primarily the different purpose of each section) but did not define how they were different. He concluded: 'This is not to say that the conditions for detention under section 2 are not demanding. Just that they are less demanding than for section 3. It would not be appropriate for me to try to define the differences between those sections. The language used is everyday language that merely has to be applied. But it has to be applied in a context that requires detention to be strictly justified.' (3) The tribunal decision was set aside because, faced with a medical report which had wrong language and a confused focus, the tribunal had failed to analyse the evidence to ensure that the doctor’s opinions could properly be related to the relevant criteria. (4) The tribunal had been asked to make a recommendation so its failure to explain its refusal was an error of law, albeit not of a kind to justify setting aside a decision (rather, a tribunal could amend its decision by adding the explanation).
8. I accept the arguments of both counsel that there is a difference between the criteria in section 2 and section 3 and that this difference is reflected in the criteria under section 72(1)(a) and (b).
9. The most significant factor leading to this conclusion is the purpose of sections 2 and 3. Detention, for whatever purpose, involves a deprivation of liberty. As such, it must be strictly justified. Once it is known that a patient requires treatment for the effects of a mental disorder, the criteria can be, and are, appropriately exacting. But detention for assessment must, of necessity, be less exacting, since the need for treatment is not then known. Assessment under section 2 may, as an essential preliminary to establishing the need for treatment, be necessary in order to render section 3 effective for some patients. To that extent, it plays an important role in protecting the health and safety of those patients and the protection of others. This does, of course, reduce the protection for the patient, but that is balanced by the fact that, unlike section 3, detention under section 2 is limited by the need for an assessment and for a period of 28 days.
10. The difference in the language of the sections reflects the difference in purpose. For the purposes of this case, the key difference is that under section 2 the mental disorder must warrant detention and the patient ought to be detained for health, safety or protection, whereas under section 3 the mental disorder must make detention appropriate and necessary for health, safety or protection. The terms relevant to section 2 are less exactly on their own and in their context. The context is related to their purpose.
11. The caselaw supports a difference. Mr Pezzani cited R v South Thames Mental Health Review Tribunal, ex parte M  COD 38. Collins J there decided that if a patient had been detained under section 2 at the time of the application to the tribunal but was detained under section 3 at the time of the hearing, the tribunal had to apply the criteria relevant to the latter rather than the former. As Mr Pezzani argued, that would not be necessary if the criteria were the same.
12. The history of the mental health legislation also supports this analysis. As Mr Pezzani pointed out, the difference in language between section 72(1)(a) and (b) was new to the 1983 Act. The equivalent provisions of the Mental Health Act 1959 – sections 25(2) and 26(2) – did not draw the distinction. It may be that the change of language was brought about by the decision of the European Court of Human Rights in Winterwerp v The Netherlands (1979) 2 EHRR 387.
13. This is not to say that the conditions for detention under section 2 are not demanding. Just that they are less demanding than for section 3. It would not be appropriate for me to try to define the differences between those sections. The language used is everyday language that merely has to be applied. But it has to be applied in a context that requires detention to be strictly justified.
20. Ms S asked the tribunal to make a recommendation. It did not do so, but according to Mr Pezzani it undertook to say why in its reasons. It did not do so. The tribunal’s undertaking is irrelevant. Ms S asked the tribunal to make a recommendation and it should have explained why it did not do so, whether the tribunal gave an undertaking or not. That failure is an error of law. but it is the sort of error that does not justify setting aside a tribunal’s decision. The proper course would be for the First-tier Tribunal to review the decision and then to amend its reasons under section 9(4)(b) of the Tribunals, Courts and Enforcement Act 2007 by adding the necessary explanation.