"I don't want any mistakes made at all," Stacy said. "I don't want them getting out of this in any sort of way. They need to pay for taking my son away from me."
Asked whether he supported prosecutors seeking the death penalty against the couple, Stacy said, "death penalty if they can."
The 35-year-old said he plans to attend the trial.
The boy's death has sparked outrage across Utah, where Ethan came to spend the summer with his mother as part of visitation outlined in his parents' divorce decree.
Joe Stacy had hoped Ethan would grow up in Virginia, in the small mountain burgs where he spent his own youth.
Instead, his son has come back under the saddest of circumstances.
Hundreds of mourners filed into the Grundy Funeral Home, which sits in two rectangular red-brick buildings on Main Street amid the lush green Appalachian Mountains that tower over the coal town of about 1,100 people. The community is nestled along the Levisa Fork River, which has flooded nine times since Grundy's inception and is again barely contained in its tree-lined banks.
Inside the funeral home's chapel, three ceiling fans cycled the humid Virginia air as pictures of Ethan flashed across a white screen that hovered above his cobalt blue casket. While Sarah McLachlan's voice soothed "You're in the arms of the angel/May you find some comfort here," photos chronicled Ethan's life from just after birth to hiking, fishing and clowning around with his dad. Some whispered "Isn't that sweet?" at a picture of a beaming Joe Stacy with Ethan in a carrier strapped to his back, while a picture of Ethan with shaving cream on his cheeks and chin elicited chuckles.
The white, pew-lined room filled with sniffles and stifled sobs as minister Mike Rife led the 180 mourners in prayer.
"You know our hearts are in a million pieces, but there is no doubt in my mind you can put together all these hearts," offered Rife, minister of the Church of Christ of Vansant, a neighboring Virginia town.
At least 300 people paid their respects throughout Tuesday's public service in Grundy, but five stuffed bears sent from Utah showed sorrow for Ethan's death was spread even wider.
The Grundy Funeral home had 7,000 page views on its website in four days, funeral director Curtis Mullins said. The site usual garners 3,000 views a month.
Stacy said he has gotten "many, many condolences" from people online and is starting to receive letters, cards and donations from all over the country.
"It's a wonderful feeling there are so many good people out there," he said.
Anthony Hensley, a cousin of Joe Stacy, said Ethan's death was "hard to believe," but the outpouring of support from places such as Utah has offered solace to the family.
Mullins said there have been more than 450 condolences posted on the funeral home's website, and he plans to have them printed in a book for the family.
Ethan will be buried in Clinch Valley Memorial Cemetery in Richlands during a funeral Wednesday, three weeks after his mother signed divorce papers in Florida and brought him to Utah for the summer.
Ethan had been in Layton for one week when, police say, on May 5 31-year-old Nathan Sloop severely beat the child on the head and face.
Nathan and Stephanie Sloop, 27, married the next day at the old memorial courthouse in Farmington, leaving the boy locked in a bedroom without medical attention, according to a police probable cause statement. Investigators say Ethan was also badly burned by Nathan Sloop before his death four days later on Mother's Day.
The Sloops allegedly disfigured his body and buried him off a trail near Powder Mountain Ski Resort, then reported him missing.
Authorities say the couple admitted to the location of his body after a 12-hour search.
Davis County Attorney Troy Rawlings said his office is waiting autopsy results and testing of other key evidence before filing charges against the Sloops.
"The primary thing we are waiting for is the medical examiner's report," Rawlings said. "Before we decide on what is the appropriate and most serious charge we can credibly file, we need to understand the cause of death."
The involvement of Ethan's mother, who initially told police she was scared of her husband, could be enough to justify aggravated murder charges against her in addition to her husband, Rawlings said.
"It's our intent to file the most serious charge, with the maximum penalty, that the facts and law allow," he said.
In Utah, aggravated murder charges can carry three penalties: the death penalty, life in prison without parole, or 25 years to life in prison with the option of parole. Prosecutors have 60 days from the preliminary hearing to decide which option to pursue.
Rawlings added that testing is continuing on fluids and tissue samples. He said he hoped the testing will be finished by May 28, when the Sloops are scheduled to again appear in court.