I am guessing you have read this:
I have updated that post with this.
By the way, many times these freak trades may not show up on the charting platforms provided by your brokerage firm. Charts are formed by the broker from the data that they receive from the exchange, typically 1 to 4 ticks per second. The actual number of trades on the exchange can be much higher in that 1 second, which means all trades that happen on the exchange can’t be shown on the chart due to this technical limitation. Check this article to read more.