Dr. Phil is standing by Burke Ramsey.
Audiences have reacted strongly to the talk show host's three-part interview with JonBenet Ramsey's brother, in particular the 29-year-old's seemingly inappropriate smiling while discussing his sister's murder. However, Dr. Phil insists Burke's smile is just a result of anxiety.
WATCH: JonBenet Ramsey's Brother and Father Address Theories of Who Killed Her: 'I Know We Were Suspects'
ET caught up with Dr. Phil on Thursday, where he spoke more about Burke, and defended him against naysayers.
"Burke is not and has never been a suspect in this case," he simply stated. "I think people have considered him otherwise because, in the very beginning, the DA and the Boulder PD have acknowledged and admitted they put out misinformation to the media, to the public, to try to put pressure on the Ramseys to either make a mistake or break or confess."
"Burke has been the missing link in this whole thing because in 20 years, he's never spoken," he continued. "He is, as I say, the only other person known in the house."
JonBenet's body was found on Dec. 26, 1996 in the basement of her family's Colorado home by her father, John, hours after police had already searched the home. John and his wife, Patsy, had initially contacted police upon discovering a ransom note demanding $118,000 for the 6-year-old beauty queen's safe return. John, Burke and Patsy -- who died of ovarian cancer in 2006 -- were ultimately cleared of any wrongdoing by police in 2008.
WATCH: JonBenet Ramsey's Brother Burke Reveals Why He Stayed in His Room After Sister Went Missing
As for Burke's critics, who find his ability to smile when talking about his sister's murder unsettling, Dr. Phil says he's just shy.
"People have commented on his smile, which is purely from anxiety," he explained. "He's kind of a loner. He's socially uncomfortable."
"When people are anxious, they do different things. They pull on their hair or fiddle around, or whatever… for him, it's a nervous smile," he said, adding that he thinks some have gotten used to Burke's seemingly odd facial expression. "I think they've gotten past that and listened to the sincerity of his answers and said, 'OK, he's just nervous.'"
Dr. Phil also offered insight into Burke's life at home, saying that while he's been "moved around" and "lived in isolation," he now "has a very nice life."
"He's a very private individual, but he has a great career and has a good relationship with his father," he shared. "They're not together all the time. They live half a country apart."
WATCH: EXCLUSIVE: Dr. Phil Asks Burke Ramsey if He Murdered JonBenet in Upcoming Interview
Instead, Dr. Phil says Burke is keeping himself busy with a job in the computer industry, and enjoying the company of his girlfriend. "He's in a relationship with a very nice young woman," he said, adding that he was shocked by Burke's "brilliance."
"He works in [computer] security, and I started asking him questions. I wasn't through the second question before he was so far beyond my understanding, I just kind of glazed over," Dr. Phil recalled. "He's very bright, very sophisticated, very well educated, and very sophisticated in what he does, and has a lot of pride in it actually."
"The interesting thing about the passage of time is you don't have to speculate about who someone is. It's been 20 years since this happened and in that time, Burke's never been in trouble with the law. He's never had any problem with assault or violence or anything like that. It's totally consistent with him not being a suspect," he concluded, before teasing viewers with what lies ahead in the final installment of his interview with Burke.
"On our final episode, what you're going to hear is Burke's very specific theory about who killed his sister," he promised.
WATCH: JonBenet Ramsey's Brother Speaks Out on Sister's Unsolved Murder Nearly 20 Years After Her Death
Part three of Dr. Phil's interview with Burke will air Monday, Sept. 19.
See more about Burke's interview in the video below.