Is This Man Caylee Anthony's Father?

Could this man be Caylee Anthony's real father? INSIDE EDITION talks to the woman who says she is certain her deceased son is Caylee's father. Could this change the course of the trial?

Could a man named Michael MacLean be Caylee Anthony's father?

That's the bombshell new claim we're hearing today. The identity of Caylee's father is one of the enduring mysteries of the Casey Anthony case.

A Massachusetts woman has come forward to say she's "100% certain" her son is the dead girl's father.

"I have no doubt," says Donna MacLean.

She says her late son often went to Florida for his work, and once told her he had a daughter with a woman named Casey.

"I said, 'Who are her parents?' and he says, 'George and Cindy Anthony.' Then he came out and said, 'And the father's a cop.' "

Casey's dad, George Anthony, is indeed a former police officer.

Donna says her son, Michael, was killed at age 24 in a car wreck in 2007.

Casey has never revealed the name of her little girl's father, but she has said the mystery man died in a car crash in 2007.

In 2008, Casey's brother Lee spoke to reporters about the man's identity.

"We will never release the name of that person that has passed away, or his family," Lee told Fox News.

Donna says she has been glued to the Casey Anthony trial. If her son is indeed Caylee's father, that would make her Caylee's grandmother.

"Are you willing to take a DNA test to determine once and for all if Caylee is your granddaughter?" asks INSIDE EDITION's Paul Boyd.

"Absolutely I would take a DNA test," Donna says.

"What do you say to people who suggest you're trying to inject yourself into this story?" asks Boyd.

"I am so not in anything like this for money. I wanted to know for me, for me and for my family," Donna says.

Caylee Anthony would have turned 6 in August.