I think the issue with not leaving a message was something from the "good o'le days" when we had land line telephones and answering machines which those in the house could hear the message as it was being left on the answering machine. The 911 dispatcher didn't want to tip off a criminal in the house that help was being dispatched if the resident was being held captive. One of things that you seen on movies a lot, and happened not as often in real life. I have been in the digital voice mail age for many years, so I am not sure if there are still machines out there which allow the message to be played as it is being left.
In my previous stint as a supervisor at a PSAP, it was mixed. Most would not leave messages with the same thought as Jim, If they need help, they would have picked up the phone or called back by now. Some would leave a message on cell phones saying that a 911 call was received from the phone and if help is needed to call back. If help is not needed, then reminding the person to lock the keypad to prevent further calls. It was an issue we had informal discussions on in the room through the years. I don't think anyone left a message on landline phones.
Getting back onto the subject, I would say yes, leave a message on wireless calls as it is a way to educate the public about the use of 911. If you do not leave a message, the public may not know that their phone called 911. When you call back, the public may not recognize the phone number you are leaving on caller ID, or some of your agencies may not leave a number. So when the citizen sees your number or "Unknown" they may think it is a sales call and not answer it. Educating the public about the use of 911 and being aware of their phone may be calling into the center inadvertantly may cause them to be more cognizant of the situation and preventing misdials in the future. I know, this may be wishful thinking for some, but if we can prevent one misdial to 911...
LP Consulting, LLCwww.copowell.com
Management, Financial, and Photography Consulting Services