"The jig is up. The puzzle pieces are beginning to fall into place, and the truth is being exposed," Police Chief Rob Davis said.
The man is from Nevada and lost a part of his finger in an accident last December, Davis said. His identity was traced through a tip made to Wendy's hot line, he said.
He said authorities "positively confirmed that this subject was in fact the source of the fingertip."
Anna Ayala, the woman who said she found the finger, was arrested last month at her suburban Las Vegas home and is charged with attempted grand larceny.
Ayala, 39, said she bit down on a 1 1/2 inch-long finger fragment while dining with her family in March at a San Jose Wendy's. But authorities had said they believed the story was a hoax.
Ayala's husband, Jaime Plascencia, was arrested earlier this month on a fugitive warrant at the couple's home to face charges unrelated to the Wendy's case. San Jose police had said he used his children's personal information in a fraudulent manner for personal gain.
Authorities are considering additional criminal charges against Ayala and her husband, Davis said.
"We are exploring all other options and avenues available to see that those involved in this charade will be investigated," Davis said.
The man who lost the finger, whose name was not released, had given the finger fragment to Plascencia, Davis said. Davis would not disclose details of the investigation but said the man was cooperating.
A phone call to Ayala's attorney on Friday was not immediately returned.
Wendy's has offered a $100,000 reward and has said it has lost millions in sales since Ayala made the claim. Dozens of employees at the company's Northern California franchises also have been laid off.