A medical practitioner or dentist chosen by a parent or guardian of a child pursuant to section 81G (1) (b) is to be present at the forensic procedure unless he or she--
(a) is unable, or does not wish, to attend, or
(b) cannot be contacted,within a reasonable time or, if relevant, within the time in which the person responsible for the effective carrying out of the forensic procedure considers the forensic procedure should be carried out if it is to be effective in affording evidence of the relevant offence.