The Medford mother of two — the one who looks vaguely familiar to people in the supermarket — knows it was wrong to have her father killed almost 31 years ago, when she was a high school cheerleader.

But she felt she had no other choice.

Cheryl Pierson, then 16, became instantly famous for all the worst reasons when a homeroom classmate she had paid shot her father, James Pierson, on Feb. 13, 1986.

Cheryl, who now goes by her married name, Cheryl Cuccio, said she hired the teen killer after her father, who had spent years raping her — sometimes several times a day — threatened to start abusing her 8-year-old sister.

She and her husband, Rob Cuccio — then her high school sweetheart — are reliving those years to promote their book about the sensational case, titled “Incest, Murder and a Miracle.” The self-published book and interviews associated with it break a decades-long silence.

“Everyone’s telling me I did the wrong thing, and I know I did the wrong thing,” Cuccio, 47, said earlier this month in her living room, Rob Cuccio, 49, by her side. “You shouldn’t kill someone.”

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But a father shouldn’t rape his daughter, and Cuccio said she had nowhere to turn. Only Rob Cuccio knew what was happening.

She said she couldn’t tell anyone at Newfield High School in Selden because her father, a 42-year-old electrician, and the principal were friends. Even now, she said, people are reluctant to believe incest victims.

“Nobody still believes anybody, whether it’s rape or it’s incest,” she said. “The word ‘incest’ . . . ”

“It’s like a four-letter word,” Rob Cuccio said.

“It’s still a dirty word,” she continued. “I’m forcing people to say the word. . . . It takes a lot to tell your dirty, disgusting secret.”

Incest is not rare. Numerous studies estimate that one in five children have sexual contact with a family member, although studies caution that incest is heavily underreported and statistics vary widely.

Laura Ahearn, executive director of the Stony Brook-based Crime Victims Center, said incest victims face unusual hurdles in coming forward. It’s not unusual for some relatives to blame the victim for the sexual relationship, Ahearn said.

An abusive parent, she said, often succeeds in creating an atmosphere in which the child feels no one will believe her or him.

Cheryl pleaded guilty to manslaughter and after an epic, dayslong sentencing hearing that detailed what she had gone through, she was sentenced to 6 months in jail.

Rob got 5 years’ probation for helping to pay the shooter $400. That teenager, Sean Pica, shot James Pierson five times in his driveway. Pica was released in 2002 after serving 16 years in prison for manslaughter.

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Cheryl’s Hauppauge defense attorney, Paul Gianelli, has remained her friend.

“She’s a very special person,” he said. After such a traumatic childhood and the crime they took part in, Gianelli said he’s impressed the Cuccios have stayed together. They had two children who are now young women — one with a degree in forensic psychology, the other in medical school.

The Cuccios have continued to look after her younger sister, JoAnn. She initially sided with the Pierson family against the Cuccios, but when she was 16 she asked to move in with them.

Rob said he and Cheryl had a 2-year-old daughter by then, but there was no question of taking her in. “I love the girl,” he said.

JoAnn reappeared a few years later — this time with her own three children — and the Cuccios again opened their door and helped her raise her kids while she put her life back together. The Cuccios now share their home with a dog and six cats.

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Cheryl said she’s had no contact with Pica, although she’s aware he’s done well since getting out of prison. Pica is executive director of Hudson Link for Higher Education, an organization that helps state inmates get a college education.

The couple’s book, which also covers a nearly fatal heart attack Rob had in 2012 and their unsuccessful malpractice suit against his cardiologist, takes an unflinching look at Cheryl’s life with her father and how his sexual attacks intensified after his wife died.

After she and Rob started dating, Rob said he quickly figured out what was happening.

“I noticed things when I was at her house,” he said. “He made it apparent that Cheryl was his. He smacked her in front of me, for giving me a napkin before him.”

After Cheryl got out of jail, Rob immediately proposed, and she began living with his family. His parents were strong presences in their lives until they died in the past year.

“His parents are — were — amazing,” she said, her voice filled with emotion. “They taught me everything I know. He [her father-in-law] was the perfect example of a father. They took me in from the moment they met me.”

Even though they were the subject of intense media interest, including a television movie, they never left the area, while trying to live as anonymously as possible.

People would sometimes seem to recognize them in stores or parking lots, but Rob, an oncology nurse, said they’d tell people they often look familiar to others.

Now that their daughters are grown, they hope they can help others struggling with the torment of incest and abuse.

“People say they wish they did what I did,” Cheryl said. “I have to tell them what I did is wrong. . . . That’s what I struggle with every day.”