Looters of archaeological sites in the United States are often petty criminals with a history of convictions for theft and other offences. But an Arizona case has exposed a different breed of 'pot-hunters': a couple of sheriff's deputies, one of whom learned archaeology from a government scientist.

The two Yavapai County deputies lost their jobs after pleading guilty last month to a felony charge of looting an archaeological resource.

Tony Mascher and John Price will be sentenced next month in the US District Court in Phoenix for violating the Archaeological Resources Protection Act at the Kinnikinick site in the Coconino National Forest. They face possible prison sentences.

As a high-school student, Mascher opted to study archaeology under a Forest Service archaeologist in the Tonto National Forest, northeast of Phoenix. Federal authorities believe he used this knowledge for his later criminal behaviour.

After searches of Mascher's home a year ago, authorities found an extensive collection of “museum-quality” Native American artefacts. All were seized by federal agents. However, most are expected to be returned to Mascher, as he has told authorities that they were legally obtained from private land.

The sheriff's deputies were caught when an Arizona State University archaeology graduate student, Wesley Bernardini, discovered them digging at the isolated Kinnikinick site. Using their legal knowledge, the deputies delayed a search of their camp-site and vehicles until late at night. The authorities believe this allowed them to throw away incriminating artefacts. When federal agents finally examined the camp-site, they found it surrounded by discarded pieces of pottery, some of which matched freshly excavated artefacts from Kinnikinick.