The five years it took regulators to bring high-profile charges against a U.K. trader underscore how hard it is to spot wrongdoing in fast-developing markets, and may herald problems in detecting future mishaps.

Navinder Singh Sarao, 36, was arrested in London on Tuesday, charged with market manipulation and wire fraud. Authorities sought to link his activities to the May 6, 2010, so-called flash crash when about $1 trillion was temporarily wiped out from U.S. stock markets in a matter of minutes.

The CME Group, the platform Sarao used for his trades and also a self-regulatory organization, first started talking to him about his trades in 2009, but he continued his alleged manipulation well into this year.