HONOLULU (KHON2) — The court case against Lehua and Isaac Kalua for the death of their adopted daughter Isabella will likely present testimony from a key witness, her 12-year-old sister.

KHON2 spoke with experts about the challenges prosecutors face in proving their case.

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Legal experts say there are a couple of things that could lead to problems for prosecutors. It’s a combination of having such a young star witness and not having Isabella’s body as evidence.

A grand jury indicted Lehua and Isaac Kalua for the murder of six-year-old Isabella, also known as Ariel Sellers. Prosecutors say Isabella’s 12-year-old sister told investigators that Lehua duct taped the six-year-old’s mouth and nose, which caused her to lose consciousness and die.

Defense attorney Megan Kau says prosecutors have an uphill battle proving their case with key testimony from a 12-year-old.

“The defense attorney is going to try to show that the witness is either not credible, she’s not believable, her perception is mistaken or her memory is just bad. Because by the time this case is tried, years will have passed,” said Kau.

She adds that getting the sister to testify in court will be a challenge because she will have to face her adoptive parents in the courtroom. But retired deputy prosecutor Ricky Roy Damerville says a 12-year-old will have plenty of credibility and strength to testify.

“Younger witnesses can be more powerful. For one reason, they don’t have a long life history of other misbehavior. That child could potentially be a very powerful and convincing witness,” said Damerville.

Damerville led the case against Jaylin and Peter Kema for the death of their six-year-old son “Peter Boy” on the Big Island. Key testimony from that case, which never went to trial because of a plea deal, was from Peter Boy’s sister.

“She was four years old when she saw Peter Boy dead in a box in the house. That four-year-old, the sister, she stuck to the basis of the story throughout her life, from the time she was four,” said Damerville.

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He says finding Isabella’s body would help but is not absolutely necessary — and it’s still possible. Honolulu CrimeStoppers just announced that the reward for any information on the case is now $15,000.