An ‘Irish Heiress’ Conned Him. He Started a Podcast to Track Her Down.

She posed as a down-on-her-luck heiress who was battling with her Irish family over an exorbitant inheritance. Sympathizers lent her tens of thousands of dollars.

But Marianne Smyth, who was born in Maine, was not an Irish heiress, and there was no fortune. She has been accused over the years of using elaborate deceptions to swindle hefty sums of money in schemes that led to two felony convictions.

Now Ms. Smyth, 54, is facing more accusations, this time from the authorities in the United Kingdom, who are seeking her extradition from the United States. The charges, for fraud and theft, date from March 2008 to October 2010, when Ms. Smyth was living in Northern Ireland, according to a complaint filed in federal court in Maine. She was arrested last month in Maine, the U.S. Marshals Service said.

The arrest was “a miracle,” said Johnathan Walton, a Los Angeles-based reality television producer who has made it his personal mission to expose Ms. Smyth, after she was convicted of stealing more than $63,000 from him.

“This woman is a career conwoman,” Mr. Walton, whose credits include “Shark Tank” and “American Ninja Warrior,” said in an interview. “There are people who spend their lives masquerading as other people to trick you.”

A lawyer listed for Ms. Smyth in court documents did not immediately respond to emails and phone messages seeking comment.