The slaying of a West Gardiner woman in 1973 and the subsequent efforts by investigators and her family members to keep the man who did it locked up will be the subject of a real crime television show airing this Thursday.

The grisly murder of 18-year-old Debra Dill went unsolved for almost 20 years.

Only in 1988 did investigators determine that, on that early September night many years earlier, Michael Boucher Sr. had beaten Dill with a hammer and left her body in the Litchfield woods. Dill had been driving home from the Lewiston Fair when her car was struck by one operated by Boucher, police later determined. He killed her after she got out of the vehicle.

Boucher was incarcerated in Connecticut for beating a woman when investigators made the connection. In 1991, he was convicted and sentenced to life in prison for Dill’s murder.

But that was just the beginning for Dill’s family members, who have fought to keep Boucher incarcerated by testifying at his parole hearings over the last 15 years.

The last hearing was in 2014, when Boucher was denied parole after Vicki Dill, one of Debra’s younger sisters, presented a petition with nearly 1,500 signatures from people who wanted Boucher to stay behind bars. At the time, various state officials also spoke out against his release.

Boucher will again be eligible to request a parole hearing in 2019.

That saga will be documented on this week’s episode of “Motives & Murders: Cracking the Case,” a show airing at 9 p.m. Thursday on Investigation Discovery, a network affiliated with the Discovery Channel. The Toronto production company Cineflix sent a crew to Maine to interview relatives of Dill and the detectives who pursued her killer.

They did not try to interview Boucher.

The current season of the show is focused on both the investigation of crimes and the families whose lives have been shaped by the murder of a loved one, according to Ron Simon, the show’s executive producer. While Dill’s story will be familiar to some in central Maine, Simon said the episode will be more targeted to a national audience unfamiliar with the details.

“No one wants to feel the pain that these families have, but everyone wants to understand that there is hope if they do have a loss,” Simon said. “(Dill’s) family exemplifies how life does move on, but you never leave behind the one you lost.”

The producers interviewed Dill’s mother, Janice Kelman, and two sisters, Vicki and Cindy DiRusso — all three of whom have testified against Boucher’s release at his parole hearings.

While Boucher has written the family a letter of remorse, they still believe he could commit another attack if released from prison, according to Vicki Dill.

“He was sentenced to life in prison. We should just let him stay there,” she said.

The family agreed to do the show in part to keep memories of Debra alive and in part to give other families hope that cold cases can be solved.

“There were nice parts,” Vicki said of recalling her sister’s life during interviews. “But there were also questions that were tough and you would cry, and it was hard living that again.”

Vicki was 10 years old at the time Debra was murdered, and the show will also highlight how her parents did not discuss the murder with her and Cindy for much of their childhood. That’s another factor she hopes viewers can learn from.

“I don’t know that [my parents] understood how to deal with this. It was too difficult and too horrific. It was too much for the family to bear,” Vicki said.

For those families who are dealing with a cold case, she went on, “Don’t let it be a wedge. Talk. Stay in communication. That process is a lot better healing than going at it by yourself or wondering or guessing.”

Charles Eichacker — 621-5642

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Twitter: @ceichacker