Someone is calling residents posing as a Dakota County sheriff's deputy and asking them to send him money.

Authorities said the impostor, who commonly uses the name Lt. John Martin but may also use others, usually tells residents that they have failed to serve jury duty and a that warrant will be issued for their arrest unless they pay a fee — usually several hundred dollars in the form of a prepaid card, according to a news release from Chief Deputy Tim Leslie.

Leslie said about a dozen residents, mostly in Inver Grove Heights, have gotten the calls. Nobody he knows of has fallen for it, he said. Inver Grove Heights police have written six police reports on it; the Sheriff's Office has written one.

Apparently the scam is a nationwide one, Leslie said. A Google search found "Lt. John Martin" scams in Tennessee, Texas, California and Florida. In each state, police have warned residents about the calls.

A Dakota County sheriff's captain called the local number the scammer has been calling from — likely a throwaway cellphone — and talked to him.

"He made a very crude remark about my captain's wife," Leslie said. "The captain told him we're going to find him and hold him accountable."

Leslie warned residents to not send money to the impostor under any circumstances. Law enforcement agencies never ask for money over the phone, the news release said.

In addition, "It's not a crime to miss jury duty," Leslie said. "We don't call people for missing jury duty."

Residents who receive calls are asked to collect as much information about the impostor as they can, including telephone numbers or addresses he may provide, and call the sheriff's investigative division at 651-438-4720.

Pat Pheifer