The voice of Oprah Winfrey, familiar to millions around the world, asks, "Can bipolar disorder cause this?"

Then the quavering voice of Andrea Petrosky tells a 911 dispatcher, "I've just killed my son."

Today, almost a year after she pleaded guilty to the first-degree murder of her 6-year-old son, Garrett, Petrosky will speak about her ordeal on "The Oprah Winfrey Show," which airs at 5 p.m. on WSET (Channel 13).

On Sunday the Oprah.com Web site repeatedly flashed a photo of the former Roanoke resident, an attractive, bespectacled blonde, sitting with her towheaded son, surrounded by Christmas presents. The caption beside the picture read, "Can bipolar disorder cause a mother to kill her child? Hear one suburban mom's story."

Petrosky, 41, wants to get the message out that mental illnesses such as bipolar disorder need to be recognized and treated rather than ignored in hopes the symptoms will go away, said Jay Finch, one of the state capital defenders who worked on her case.

Though he was not interviewed for the segment airing on "The Oprah Winfrey Show," Finch was contacted by a producer about Petrosky's case about a month ago, he said. He later received a letter from Petrosky that indicated she had been contacted by the show.

Contacted by phone Sunday, Finch recalled speaking to Petrosky during the week following her Oct. 16 guilty plea. "She made it clear to me, if I were ever in a position to use her story to educate people on mental illness and how it can impact a family ... that she wanted me to do it."

Petrosky and her family lived in Roanoke for several years before moving to Bristol in 2004. Her husband was a pharmacist at Brambleton Drug. Her daughter attended Patrick Henry High School. Garrett went to Salem Montessori School.

She had a reputation as a "supermom," involved in all her children's school activities, working toward a degree at Radford University while managing the clothing and accessory store Present Thyme.

Then on April 15, 2005, she kept her son home from school. As they watched a cartoon together, she grabbed him by the neck and choked him until he stopped struggling. Then she took him to the bathtub, which she had already filled, and put him under the water.

She called 911 and said over and over, "I've just gone crazy."

Had her case gone to trial, a jury would have heard opposing testimony from two psychologists. Defense expert Dewey Cornell had diagnosed Petrosky with a form of bipolar disorder and concluded she had hallucinations in which she heard voices. The prosecution's expert, while conceding Petrosky had a history of mental illness, would have testified she was legally sane when she killed her son.

"I do not know why I did this," she said in her confession to police, presented in court the day of her plea. "My thoughts are out of control, bad thoughts. I'm just crazy I guess. I should have called someone and asked for help, but I didn't."

When Petrosky pleaded, she avoided a possible death sentence under a Virginia law that makes it a capital crime for an adult 21 or older to kill a child under 14. She is serving 42 years of a 50-year prison sentence.

The type of bipolar disorder Petrosky was diagnosed with, referred to as bipolar disorder II, is not always apparent to the families and friends of the person who has it, but can be more severe when it reaches psychotic levels, Finch said. Most people with the disease "will never have a breakdown similar to the one Andrea had, but a percentage of them will," about one in 20, Finch said.

Petrosky has recently been selected to help run a prison ministry outreach, her attorney said. "She's tried to make the best of the time remaining in her sentence."

She has told Finch that "her heart breaks even more every day thinking about Garrett."

The Rev. David Stancil, pastor of First Baptist Church in Bristol, said he and others had been contacted by an acquaintance who knew of the upcoming show and asked for prayer on Petrosky's behalf.

The request came out of "compassion for somebody who's having to deal with the aftermath of this for the rest of her life," Stancil said.

The murder of Petrosky's son stunned many who knew her in Bristol and Roanoke.

"She was broadly liked," Stancil said. In the weeks following her crime, some young mothers in the community found themselves asking troubling questions, he said: "Gosh, if Andrea could do that, could I do that? Could that kind of darkness be in my life, too?"