The mother of three missing Michigan boys is asking a judge to declare them dead nearly 15 years after their disappearance.

Tanya Zuvers told a Lenawee County judge Monday that while their bodies were never found, her sons deserve the respect of a proper headstone. She’s seeking official death certificates for closure.

Andrew, Alexander, and Tanner Skelton vanished in 2010 while visiting their father, John Skelton, over Thanksgiving. He’s long been suspected but never charged in their deaths. Skelton is set to finish a 15-year prison sentence this year for failing to return the boys to their mother.

Investigators testified they’ve exhausted every lead, including DNA testing and extensive searches. A former police chief said he’s confident the boys are deceased.

Skelton, appearing by video from prison, refused to participate, saying nothing he says would change the outcome. The judge is expected to rule on the request this week.