Te'o rose to national prominence while leading Notre Dame's Fighting Irish to an undefeated regular season. As he and his team excelled, Te'o told interviewers in September and October that his grandmother and girlfriend, whom he described as a 22-year-old Stanford University student, had died within hours of each other.

"I miss 'em, but I know that I'll see them again one day," he said then.

An online relationship

Last week, Te'o told talk show host Katie Couric that Tuiasosopo had called him the day the story broke to confess.

During that interview, Te'o said he doubted the voice he knew as Kekua was a man's voice.

Tuiasosopo has said he faked his voice to sound feminine. In the interview, McGraw questioned his veracity and repeatedly challenged him to prove it.

McGraw said his show had contacted private contractors for the FBI and the Secret Service, giving them a voice mail message that Tuiasosopo said he had left for Te'o. "They looked at everything from voice intonation to tonal qualities" and concluded that "the chance that you are the person on that voice mail is like one in 10 million," McGraw said.

Tuiasosopo insisted he was telling the truth but said he would be uncomfortable talking in his feminine voice for the TV host. "I've never done it in front of people," he said.

Tuiasosopo' s state of mind

Psychotherapist Robi Ludwig said the behavior described by Tuiasosopo to McGraw is very possible.

"We see this with Internet dating. Sometimes people lie," Ludwig told CNN's Erin Burnett OutFront.

"It's a place where they can experiment and where they can impersonate the other sex."

Ludwig said it is possible that Tuiasosopo "actually did have a crush on Manti Te'o and was confused about his sexuality."

"And the reason why he impersonated this woman was to see what it would feel like to be intimate with Manti Te'o, to be loved by Manti Te'o," she said.

"Who would say this if it weren't true? I don't get the sense that he's a sociopath. I get the sense that he's confused."