I guess the perpetrators might be found by correlating the buyer/seller data from a number of cases where fraud is reported.
The perpetrators could try to make this more difficult by making the data harder to correlate; pump some stocks that they don't buy or sell, pump some stocks, but intentionally sell outside the obvious window of opportunity, possible at a (small) loss, using multiple, unrelated accounts to buy and sell the stock, etc.
That way, the detectives have to try to find multiple unrelated perpetrators (from their point of view, because of the separate accounts), that have made a significant profit in some of these cases.
I think it's going to take a whole lot of very interesting data mining to find them, based on the stock data only.