After any unusual drop or rise in value, a circuit breaker must be implemented.
Reads to me that as soon as there is an "unusual" change in the price, then trading should be stopped. i.e. the suggestion of the OP is that the trigger is the higher than usual price fluctuations.
This is the definition of limit up / down.
If there is suspected fraud then that is another matter altogether.....My point is that the trigger can not ONLY be price up/down.