"The Justice Department charged the United Kingdom's Navinder Singh Sarao with wire fraud, 10 counts of commodities fraud, 10 counts of commodities manipulation and one count of spoofing (which is when a trader places a bid or offer with the intent to cancel before execution)." - Everett Rosenfeld, "UK trader charged for manipulation contributing to 2010 flash crash," in CNBC, April 21, 2015. Here is the coverage.
This alleged financial Machiavelli earned profits of about $40 million from that particular scheme. However, there has been much more than that. Allegedly he had been engaged in similar but less spectacular market-moving activities between 2010 and as recently as this year.
Like the Ponzi configuration of Bernie Madoff, this was complex. For example, Sarao used "layering." That is an elaborate kind of spoofing. It creates the illusion that there have been many orders at various prices. In usual spoofing there is only one fake price.
Some are shocked that it took so long to catch up with Sarao. That it did can encourage other market manipulators to continue with the fraud.
Perspective from BusinessInsider. Read here.