There have been no charges filed in the "suspicious" June 2012 death of 3-month-old Colin Eugene Russell, who Marion County investigators have said died from possible brain trauma.
The holdup in completing the investigation is a final autopsy report.
Marion County Sheriff Ronnie "Bo" Burnett said he wasn't sure why the state medical examiner's final report still is not complete. He said county investigators turned over all their paperwork to the state office in Nashville.
Burnett said he didn't think there were any problems with the case, just that it appeared it was taking time to wrap up the medical information.
Mike Taylor, district attorney for the 12th Judicial District, said medical reports on small children and infants seem to take longer than those on adults.
"I don't really know why," he said, speculating that it might take longer to rule out some causal factors for the youngest victims.
Burnett and Taylor said there has been no change regarding a "person of interest" in the case, the baby's father, Chris Russell. Officials said the baby's mother, Leah Collins, has not been named a person of interest so far.
Woody McMillin, spokesman for state medical examiner Dr. Karen Cline-Parhamovich's office, said Friday that he was unable to reach her to find out the report's status.
The investigation began June 17, 2012, after family members made an emergency call when the infant stopped breathing.
The baby was taken to Grandview Medical Center in Jasper, where he was stabilized before being transferred to Vanderbilt Medical Center in Nashville. Officials said early on that Vanderbilt staff described the baby's injuries as "major trauma" to his brain. He died after the family decided to discontinue life support June 23, 2012.
Investigators said initial medical scans and an MRI scan performed before the baby died showed he had retinal hemorrhaging and brain trauma, injuries similar to those found in cases of shaken-baby syndrome.
Early on, medical officials also found the baby had rib fractures that were "at least 10 days old," and that he had been throwing up in the days before he died, a sign of possible brain injury, officials said.
Contact staff writer Ben Benton at bbenton@times freepress.com or 423-757-6569.