(CNN) -- An Alabama judge signed an order Thursday declaring Natalee Holloway legally dead, attorneys for her family said.
Probate Judge Alan King signed the order after an afternoon hearing in Jefferson County court in Birmingham.
Holloway was 18 when she was last seen in the early hours of May 30, 2005, leaving a nightclub on the Caribbean island of Aruba with Joran van der Sloot and two other men. No one was charged in her disappearance, and her body has never been found.
On Wednesday, van der Sloot -- who was detained twice in connection with Holloway's disappearance but never charged -- confessed in a Lima court to murdering a 21-year-old Peruvian woman five years after Holloway went missing.
Natalee's father, Dave Holloway, filed a petition to declare his daughter dead in June, six years after she went to the Caribbean island with 100 classmates to celebrate their graduation from Mountain Brook High School in suburban Birmingham.
He was present at Thursday's hearing, as was his ex-wife, Beth Holloway. She opposed the move to declare Natalee dead, pointing to a lack of evidence indicating her daughter is deceased and saying in a September statement that she "will always hope and pray for Natalee's safe return."
On Thursday, she told reporters while leaving the courtroom that she was upset by the judge's decision.
"Natalee's father wanted to see this through, and of course it makes me very sad," said Beth Holloway, who now works with groups and families of missing children.
Dave Holloway acknowledged Thursday that the ruling is "tough," though he said he's considered it a possibility ever since the FBI told him 10 days after his daughter went missing that they were approaching her case as a homicide.
"We've been dealing with this death for the last six and a half years," he told reporters Thursday. "Hopefully, this meeting today will (provide) some closure."
In a hearing in September, King ruled the petition could go forward, according to CNN affiliate WBRC.
At that time, King ruled that a notice of presumption of death must be published in a local newspaper for two successive weeks, followed by a 12-week time frame to submit any evidence the teen is still alive, WBRC said. Barring any such evidence, the judge would then be able to declare Natalee Holloway dead.
Dave Holloway explained that, barring his daughter miraculously being found alive, that a decision like the one issued Thursday had to be issued "eventually."
His attorney, Mark White, previously said that the order -- which acts as a death certificate -- will help resolve the estate of Natalee Holloway, who still has a small college fund in her name and is listed as a participant and beneficiary on her father's health insurance.
Now was the proper time to pursue this action, said Dave Holloway, given his desire to take "care of some needs" and van der Sloot's conviction earlier this week.
"I was in a situation where a lot of things came together, with the criminal element as well as having to take care of business," he said.
The 24-year-old Dutch national could be imprisoned for as many as 30 years when he is sentenced Friday, two days after he pleaded guilty to all the charges against him in the killing of a Peruvian woman in 2010.
Investigators believe van der Sloot killed Stephany Flores after she found something related to the Holloway case on van der Sloot's computer as she visited with him in his hotel room.
Van der Sloot also faces possible extradition to the United States. In June 2010, a federal grand jury in Alabama indicted him on charges of wire fraud and extortion after allegations surfaced that he tried to extort $250,000 from Holloway's mother. Van der Sloot offered to provide what turned out to be bogus information about the whereabouts of Natalee Holloway's remains in exchange for the money, according to the indictment.
He was allegedly given a total of $25,000, and authorities believe he used that money to travel to Peru and participate in a poker tournament, where he met Flores.
Peggy Sanford, a spokeswoman for the U.S. Attorney's office for north Alabama, said that there's no timetable as to when federal authorities will seek to bring van der Sloot to the United States for prosecution.
"We want Joran van der Sloot to face the charges here, and we are prepared to try him as soon as we can get him to the United States," Sanford said. "Right now, we don't know when that will be."
InSession's Jean Casarez contributed to this report.