More than three years ago, a little boy named David Roberts collapsed at a daycare on North Whidbey. He died a few days later.

The unresolved tragedy on North Whidbey and a state agency’s response spawned a lawsuit that recently moved to federal court.

Doctors found that the 2-year-old suffered a fractured skull and a subdural hemorrhage, but nobody could — or would — explain how it happened. Doctors and the medical examiner disagreed on the timing and cause of the injury, a detail that would become crucial in the investigation into the death.

While the boy’s parents and experts on child abuse were convinced that it was a homicide that occurred at the daycare, the detective handling the case, a prosecutor who reviewed the investigation and the medical examiner concluded that there wasn’t evidence to determine if the manner of death was an accident or homicide, let alone who may have caused it.

In the end, the case went cold.

Then, earlier this year, the couple who ran the daycare filed a lawsuit against the state Department of Social and Health Services, or DSHS, for removing their children from their home for about two weeks following the boy’s death.

The lawsuit, brought by Raquel and Nicholas Eliasen, alleges that state officials improperly removed the three children from their home, causing the family “severe and lasting harm.”

“My clients feel their children were wrongly and inappropriately taken out of the house without adequate and appropriate investigation by the state,” said Joe Shaeffer, the Eliasens’ attorney.

This is the second lawsuit related to the boy’s death. In 2015, the Roberts filed a lawsuit against the Eliasens in Skagit County District Court; it was subsequently moved to federal court and appeared to have been settled out of court, documents show.

The lawsuit claims that the boy’s injury clearly happened at the daycare and faults the Eliasens. The complaint cites a doctor at Harborview Medical Center in Seattle who concluded that the child would have lost consciousness immediately after the injury because of its catastrophic nature.

The lawsuit also states that parents who brought their children to the daycare weren’t notified that Nicholas Eliasen had been convicted of burglary and had “anger management issues.”

Detective Ed Wallace with the Island County Sheriff’s Office is likely to be an important witness in the Eliasens’ lawsuit if it moves forward. He investigated the case and concluded that the children should not be removed from the Eliasens since there was no reason to believe they were in danger, but DSHS officials went around him and obtained an order from a superior court judge.

“I didn’t believe there was a reason to take the kids out of the home,” he said. “I still can’t even say for sure that a crime was committed.”

DSHS officials, however, relied on the opinion of Dr. Kenneth Feldman, a physician who is board-certified in child abuse pediatrics and consults on child abuse issues, according to his biography at University of Washington Medicine. Feldman concluded that the injuries were caused by child abuse that could only have happened at the daycare, according to investigative files.

The lawsuit, however, alleges that DSHS knew Feldman “has a reputation among some in the medical community and beyond for assessments that unfairly malign parents,” noting a 2002 Seattle Post-Intelligencer investigation.

In addition, the lawsuit claims DSHS officials knew about conflicting opinions from other experts but didn’t present that evidence to the judge.

Shayna Roberts, David’s mother, wrote in an email to the Whidbey News-Times that she believes that the evidence is clear that “the Eliasens” inflicted the fatal head trauma.

Wallace’s report on the case, reviewed by the News-Times, summarizes the evidence and the investigation.

David Roberts had symptoms of autism and development disabilities when he was younger, according to the case file. He was at the Little Rascals Daycare near the Navy base on North Whidbey when he reportedly screeched and collapsed in the afternoon of Jan. 18, 2013; the Eliasens called 911 and administered CPR.

The boy was transported to Whidbey General Hospital and then Harborview Medical Center in Seattle, where he later died.

The cause of death was determined to be a skull fracture and subdural hemorrhage from blunt force injury to the head. The manner of death remains undetermined.

In the subsequent investigation, Wallace received reports from three different pediatric doctors who reviewed the medical evidence, including an expert at Walter Reed. They all concluded that it was highly likely, given the timeline, the injuries occurred at the daycare and were inflicted by an adult.

A pathologist in the King County Medical Examiner’s office, however, concluded that the injuries could have occurred as much as 24 hours prior to the boy’s collapse and that they couldn’t rule out accidental injuries.

Based on the pathologist’s timeframe, Wallace’s investigation focused on the five adults who were around David Roberts in that time period. In addition to the Eliasens and the Roberts, a man had picked up a child at the daycare while the boy was there.

Wallace pointed out that the case wouldn’t be solved even if there was conclusive proof that the boy was injured during the time he was at the daycare. Investigators wouldn’t be able to point to one suspect or to a manner of death — whether it’s homicide, negligence or an accident.

Chief Criminal Prosecutor Eric Ohme reviewed the investigation and declined to file charges, noting “equivalent evidence” that any of the adults caused the injuries.

“In summary, there is no hard evidence that any particular adult caused David’s injuries,” he wrote, also noting the possibility of an accidental injury.

A spokesman for DSHS said the agency could not comment on impending litigation. The state Attorney General’s Office is representing the agency and moved the lawsuit from Island County Superior Court to U.S. District Court. Along with negligence, the Eliasens’ lawsuit claims a violations of Fourth and Fourteenth Amendments rights.

While Wallace may be drawn into the lawsuit, he said what most haunts him is the fact that the little boy’s death remains an unsolved mystery — one which he still hopes to solve someday.

“My only duty and desire is to find out what happened to David,” he said. “I want closure for him.”