Hilo man sentenced to 30 years for 2022 kidnapping of 2 teens, sexual assault of 15-year-old Kona girl

Duncan Mahi of Hilo was sentenced on Friday in Kona Circuit Court to 30 years in prison for abducting a 15-year-old Kona girl and her boyfriend at a West Hawaiʻi beach and sexually assaulting the girl in 2022.

The 54-year-old Mahi negotiated a plea deal on Dec. 31, pleading no contest to first- and second-degree kidnapping and first-degree sexual assault from an incident that occurred on Sept. 16, 2022.

Mahi robbed two teenagers at knifepoint at Anaehoʻomalu Bay in West Hawaiʻi. According to court documents, Mahi forced the girl to tie up her teen boyfriend before he took her to his East Hawaiʻi home.

Kona Circuit Court Chief Judge Wendy DeWeese sentenced Mahi to 20 years and 10 years in prison for each of the two kidnapping charges, which will run consecutively for a total of 30 years and a mandatory minimum sentence of 20 years behind bars.

She also sentenced Mahi to another 20 years in prison for the sexual assault charge, to be served at the same time as the kidnapping charges.

DeWeese told Mahi prior to handing down his sentences, according to a KHON2 report, that she found Mahi’s behavior described in pre-sentence investigation documents and by the victims as evidence that his actions in September 2022 “were planned and predatory and not spur-of-the-moment driven by your drug use,” she

“And while Iʻm sure drugs played a role, you cannot blame your actions on drug use,” DeWeese said during Friday’s sentencing hearing.

Mahi must also pay $1,010 to the crime victims fund.

He declined to address the court during Friday’s sentencing hearing.

“Once I sentence you in this case this will be over for you,” DeWeese said, according to KHON2. “But the victims and their families will continue to suffer the consequences of your selfish and cruel actions.”

According to police, Mahi forced the girl to tie up her teenage boyfriend, smoke methamphetamine, perform sexual acts and then took her to his East Hawaiʻi home.

The case prompted the first use ever, at the time, of the MAILE AMBER Alert system on the Big Island in its nearly 20-year history in Hawaiʻi.

The 15-year old was able to escape from Mahi nearly 24 hours later after convincing him to take her to get food at Café Pesto in Hilo, where an employee of the restaurant recognized the teen and was able to rescue her.

KHON2 reported the victimʻs family on Friday praised the victim for her quick thinking, which ultimately opened the door to her escape.

“I really want to commend her for really saving herself in this situation. She was so smart, so brilliant,” her mother told KHON2. “She manipulated and outsmarted her abductor and she is her own hero.”

They also thanked Bridge Hartman, the Café Pesto employee who recognized her from the MAILE AMBER Alert, and Cori Takaki for both helping with rescuing her at the Downtown Hilo restaurant.

The victim’s mother thanked Hawaiʻi Island police and fire departments, prosecutors, family, friends and Judge DeWeese.

“I’d like to recognize the bravery and courage of our survivors. I hope today’s sentencing offers them and their families some closure and a sense that justice was served,” said Hawaiʻi County Prosecuting Attorney Kelden Waltjen in a statement. “Hawai‘i Island is a Big Island but a small community. We come together, we lean on each other for strength, and that’s what makes us resilient.”

Mahi was initially charged with 11 offenses. He was indicted Sept. 21, 2022, by a Hilo grand jury.

Prosecutors dropped the other charges of first- and third-degree sexual assault, methamphetamine trafficking, two counts of first-degree robbery and two counts of first-degree terroristic threatening as part of a plea deal with Mahi.

KHON2 also reported that the victim is ready to move on and has plans to attend college.

“I think she’s the bravest one here,” KHON2 reported Hartman saying about the victim.

News reporter Nathan Christophel contributed to this story.