Opening statements are scheduled to begin this week in the trial against a man accused of murdering his teenage stepdaughter, who disappeared more than two decades ago in Arizona.

Phoenix police arrested Michael Turney, 75, in August of 2020 on second-degree murder charges, 19 years after his stepdaughter, 17-year-old Alissa Turney, vanished on her last day of her junior year of high school, according to a 2020 press conference hosted by the Maricopa County Attorney’s Office.

RELATED: Man Who Alleged Missing Stepdaughter Was Killed By Electrical Worker Union ‘Assassins’ Charged With Murder

The Paradise Valley High School student was last seen by her boyfriend on May 17, 2001, when she told him she was leaving school early and being picked up by her stepfather, then-County Attorney Allister Adel said at the press conference.

The teen had plans to celebrate graduation with her upperclassmen friends later that evening, but never made it.

“Alissa’s life was just beginning,” Adel said.

According to police, in 2001, Michael reported that his stepdaughter ran away from home, claiming Alissa left a note explaining that she was going to California. Authorities initially determined that there was no foul play involved and deemed her a runaway.

A criminal investigation into Alissa’s disappearance began in 2008, after numerous interviews with the teen’s friends and family led authorities to believe that she was not a typical runaway case.

As police narrowed in on Alissa’s stepfather as a suspect, based on details from their interviews, they issued search warrants to execute at Michael’s home, where they discovered several explosive devices.

FBI officials found 26 pipe bombs with other various explosives. They said Michael, who had worked as an electrician in the 1980s, planned to blow up a union hall, The Arizona Republic reported.

Read Related Also: Daniel Steffen Sentenced to Prison for Illegally Recording Sexual Activity

Michael pled guilty to unlawful possession of unregistered destructive devices and remained in federal prison until his 2017 release.

Alissa’s sister, Sarah Turney, never gave up on finding her sister and devoted her life to investigating what had happened back in 2001.

Sarah — the creator of the podcast “Voices for Justice,” which feature cases in need of attention — gathered information, erected billboards of her missing sister and went to social media to help solve the case of Alissa’s disappearance.

Alissa’s story gained traction on social media when Sarah made a video on TikTok as a call to action to bring justice for her sister, hoping that other TikTok users could help solve the case.

RELATED: Police Analyzing “Items” Found At Portuguese Dam in Search for Madeleine McCann

Sarah shared the news of her father’s August 20, 2020 arrest on Twitter, saying “I’m shaking and I’m crying. We did it you guys. He’s been arrested. Omg thank you. #justiceforalissa Never give up hope that you can get justice. It took almost 20 years but we did it.”

While thanking investigators on the case during the press conference, Adel also gave recognition to Sarah, saying her dedication to finding Alissa is “a testament to the love of a sister.”

“Because of your love, Alissa’s light has never gone out,” she added.

Alissa, whose body was never found, is presumed death. Opening statements are scheduled for Thursday, July 6.