UPDATE: Christopher Russell was sentenced to 25 years for each count (First-degree Murder and Aggravated Child Abuse).

The sentences will be served concurrently (at the same time). He will receive credit for time already served since his arrest.

Officials say Russell was in custody from 11/21/14 – 9/22/15 and then 8/17/16 – present, he has spent about a year in prison so far. 

PREVIOUS STORY: Jury selection begins today in the first-degree murder trial of Christopher Russell, the Marion County man accused in the 2012 death of his three-month-old son Colin Russell.

Russell is facing charges of first-degree murder and aggravated child abuse in his son's death.

The autopsy report noted contusions on the infant's head and "extensive" hemorrhaging of the optic nerves in both of the child's eyes.

There were other injuries noted in the report; over a dozen fractured ribs and a broken collarbone.

PREVIOUS STORY: Investigators are waiting on autopsy results to determine how an infant died over the weekend.

No charges have been filed, but investigators say doctors called them concerned about the child's injuries and how he got them.

"It's a bad, bad thing," said Marion County Sheriff Bo Burnett, when asked about the death investigation underway.

Sheriff Burnett calls the death of 3-month-old Colin Russell, "suspicious".

"The doctors determined he had brain damage," said Burnett, in an interview with Channel 3, "the baby passed away this past Saturday night."

An ambulance was called to a trailer home on Sequatchie Lane last week, when Colin stopped breathing.

He was taken to Grandview Medical Center, then transferred to Vanderbilt in Nashville.

"There was nothing visible," said Burnett, when asked if the child showed signs of being injured, "but the child did have some brain damage."

Detectives tell Channel 3, the infant had fractures and brain damage consistent with shaken baby syndrome.

Sheriff Burnett is waiting on autopsy results to determine if a crime was committed.

Channel 3 visited the family's home today.

Christopher Russell and Leah Collins did not come to the door.

The engaged couple has numerous pictures of them with baby Colin, born in March, on Facebook.

Sheriff Burnett says Russell has been questioned, but no arrests have been made.

He says charges could come, pending the outcome of the autopsy.

"The lead detective on this case, she's spending a lot of time on it, I wouldn't be surprised," said Burnett.

Colin's father, Christopher Russell, has been named a person of interest in the case, but it's important to note - he has not been charged.

Burnett says he plans to give Russell a lie detector test at the end of the week, but won't say why.

The Sheriff says the district attorney's office will review the case once autopsy results come back to determine what happens next.