§ 20. Charges against city officers. Whenever it is provided herein, or otherwise by law, that an officer of the city shall hold office during good behavior or shall be removed only upon charges, such charges shall be for disability for service or neglect or dereliction of official duty or incompetency or incapacity to perform his official duties or some delinquency materially affecting his general character or fitness for the office, unless otherwise specifically provided by law. Where the charges are for disability for service, the examination shall be one of inquiry only and the decision made in a proper case, may be for honorable discharge from service. In all other cases the examination shall be a trial, conducted under such reasonable rules and regulations as shall be prescribed by the officer, officers, board or body before whom the trial is held. Whenever an elective city officer shall be or become permanently disabled, or permanently incapacitated and is thereby rendered incapable of performing his official duties during the remainder of his term of office, such officer may be removed upon charges and after hearing, in the same manner as is provided herein or otherwise by law, for the removal of appointive officers of the city.