Well, generally some government employee goes to a farm every once in a while and makes sure that the producer is following all the organic standards. Generally, the system works pretty well. But if there's concern that a producer is only following organic protocols occasionally, there aren't many ways to catch them in the act.
Researchers at the University of East Anglia in Norwich have created a new test that can detect very subtle differences between vegetables grown organically and non-organically. The test actually detects nitrogen isotopes within the plant, so there's no way to wash off the evidence.
The process isn't meant to replace inspection, but it is a great backup is fraud is suspected. And as the market for organic products grow, it's important to be able to detect the differences between conventional and organic produce. Because a few perfectly beautiful apples covered in petrochemical pesticides can ruin the whole bunch. ::Discovery.com