If the two doctors do not have previous acquaintance with the patient, and the AMHP does not provide an explanation for why a doctor who knew the patient could not be found, does that make the section invalid?
I’d say impossible to determine prima facie. Would require more investigation. “Practicable” in s12(2) is a rather low bar and might be relied upon even if justification isn’t given in the section paperwork. I assume you’ve already considered the AMHP report?
According to Jones 27 Edition, 3/4 down page 108 he says
"If it is not possible to obtain a recommendation from a doctor who has had previous acquaintance with the patient, the applicant must explain on the relevant application form why this was the case. Although the Code of Practice states at para. 14.74, that it is preferable that a doctor who does not have previous acquaintance with the patient be approved under this section, this is not a legal requirement. As the key purpose of the medical recommendation is to confirm that the statutory grounds for either detention or guardianship are present and as there is no absolute requirement for one of the medical recommendations to be given by a doctor who has had previous acquaintance with the patient, it is submitted that a failure by the application to provide an explanation would not constitute a fundamental defect which would render the application unlawful.
Reference Guide:
31.23 Examples of errors capable of rectification include:
• leaving blank spaces on the form, which should have been completed,
other than the space for signing it or for recording the doctor’s reasons for
believing the statutory criteria are satisfied