Fairstein compared the fist-happy crooner to O.J. Simpson, who repeatedly beat his wife without consequence before she was slain in 1994.
Rihanna's reported reconciliation with Brown after her Feb. 8 pummeling sparked an outpouring of debate, controversy and motherly advice.
"Love doesn't hurt," Winfrey said on her show Friday, while announcing she will dedicate a program this week to discussing domestic violence.
"I want to do a show about it, dedicated to all the Rihannas of the world."
Speaking directly into the camera, Winfrey said, "If a man hits you once, he will hit you again. He will hit you again."
Sex crimes expert Fairstein warned Rihanna - as 21-year-old Barbadian singer Robyn Rihanna Fenty is known - that she risks not just another bloodying, but her very life.
"Many of the circumstances in her case were like the early warning signs in the O.J. Simpson case," Fairstein said.
She pointed to several "red flags" that suggest Rihanna could be in the same danger as Nicole Brown Simpson was 15 years ago, getting hit repeatedly but not pressing charges and then reconciling with the former running back.
The allegation that Chris Brown choked Rihanna while saying "Now I'm really going to kill you" is a particularly bad sign, Fairstein said.
"Choking behavior is a very interesting factor. It's hands on, face-to-face. It's a very intimate type of violence," she said.
New police techniques that assess an offender's potential lethality based on a list of warning factors should be used in this case, Fairstein said.
The Daily News reported this weekend that Rihanna is torn about whether to testify against Brown next month.
According to a police affidavit, the couple began squabbling after Rihanna found a text message from one of Brown's ex-girlfriends on his cell phone as they were driving through Hollywood.
Brown then allegedly punched her repeatedly, tried to push her out of the car, bashed her head against the window, bit her ear and fingers, and choked her until she nearly passed out.
Brown, 19, entered no plea last week to two felony charges of assault and making criminal threats. He is out on $50,000 bail and returns to court April 6; his celebrity lawyer, Mark Geragos, is reportedly trying to work out a plea deal.http://www.nydailynews.com/gossip/2009/03/08/2009-03-08_oprah_winfrey_has_a_warning_for_rihanna_.html