Almost two decades after the disappearance of American teenager Natalee Holloway in Aruba, the main suspect in the case, 36-year-old Dutchman Joran van der Sloot, is expected to plead guilty to murdering her later on Wednesday.

His admission is part of a plea agreement with American prosecutors, who have accused him of trying to extort money from Holloway’s mother in exchange for telling her where her daughter’s body is located.

As part of the plea agreement, which still has to be accepted by a federal judge in Birmingham, Alabama, van der Sloot will have to reveal the details about Natalee Holloway’s death and what happened to her remains in exchange for a lower sentence of 20 years.

He had previously pleaded not guilty to murdering Holloway while she was on a high school graduation trip with classmates in Aruba.

Both van der Sloot and Holloway’s family are expected to be in court to hear his confession, which comes after FBI investigators found it credible after he passed a lie detector test.

A lawyer for Holloway’s family, John Q Kelly, told NBC’s Today TV show that “there won’t be any further investigation or search … for Natalee’s remains.”

Earlier this year, Van der Sloot was extradited to Alabama from Peru, where he is serving a 28-year sentence for killing Peruvian student Stephany Flores in 2010. If the judge approves the plea deal, he is expected to be flown back to Peru.

Natalee Holloway’s disappearance and the investigation into what happened to her has made headlines for decades in both the Netherlands and the US, including a 2008 Emmy-winning broadcast by murdered crime reporter Peter R. de Vries and Kees van der Spek that was watched by some seven million people in the Netherlands.