What special training, demeanor, and other conditions should be considered by the police department interviewers?

First, make any edits necessary based on the feedback from your instructor.
Amend the general order to include caution, techniques, and skills authorized for use in obtaining statements from special populations (e.g., children, elderly, and the mentally challenged).

What special training, demeanor, and other conditions should be considered by the police department interviewers?

Do not forget about proposing possible themes on how to approach certain populations when seeking their information.
Read the literature, and do some scholarly research to develop your addendum to the earlier general order.

Your assignment should be submitted as a memorandum from the chief of police to the entire department as a supplement to the original general order. Your memorandum should include sections for the following special populations (at a minimum):

Children
The elderly
The mentally challenged
The high performer might also suggest other special populations to consider, if any.