Section 100B. Any city operating under a Plan D or Plan E charter which accepts this section by the affirmative vote of two thirds of all the members of its city council, and any other city which accepts this section by a majority vote of its city council with the approval of its mayor, and any town which accepts this section by a majority vote of its inhabitants at an annual town meeting or a special town meeting, may, upon written application by any of its police officers or fire fighters retired either before or after the acceptance of this section under a general or special law specifically relating to retirement for accidental disability, except a special law applicable to one person, or in the event of the death of any such police officer or fire fighter, upon written application by his widow or, if he leaves no widow, by his next of kin, indemnify, out of any funds appropriated for the purposes of this section, such police officer or fire fighter or, in the event of his death, his widow, or if he leaves no widow, his next of kin, for all reasonable hospital, medical and surgical, chiropractic, nursing, pharmaceutical, prosthetic and related expenses and reasonable charges for podiatry incurred by such police officer or fire fighter after his retirement; provided, however, that no person shall be indemnified under this section unless a majority of the members of a panel consisting of (a) the chairman of the retirement board of the city or town, (b) the city solicitor, town counsel or other officer having similar duties or a person designated in writing by such solicitor, counsel or officer to act for him, and (c) such physician as the city or town manager or, if there is none, the mayor or selectmen in writing appoint shall, upon receipt from the applicant of due proof, certify:—(1) that the expenses for which indemnification is sought were the natural and proximate result of the disability for which the police officer or fire fighter was retired; (2) that such expenses were incurred after the acceptance of this section; (3) that the hospital, medical and surgical, chiropractic, nursing, pharmaceutical, prosthetic and related expenses and reasonable charges for podiatry to which such expenses relate were rendered within six months before the filing of the application; (4) that such expenses were in no ways attributable to the use by the police officer or fire fighter of any intoxicating liquor or drug or to his being gainfully employed after retirement or to any other willful act or conduct on his part; and (5) that such expenses are reasonable under all the circumstances.