Depends on whom you ask.
Prosecutors portray him as an unfaithful husband who wanted a childless life, while the defense describes him as a doting dad who kissed his son every time he put him in the car.
And friends say he loved to show off the blond, bright-eyed boy and talked about him incessantly.
At a probable cause hearing Thursday, authorities provided more insight about Harris, who is charged with felony murder and second-degree child cruelty in last month's death of 22-month-old Cooper Harris. He has pleaded not guilty.
A judge denied bond for Harris on Thursday, ruling that prosecutors have enough evidence to move forward in their case.
Here's some details about Harris that emerged at this week's hearing and in court documents:
Harris allegedly sexted the day his son died
While at work June 18, Harris messaged six women, according to Cobb County police Detective Phillip Stoddard, the prosecution's lead investigator. He allegedly exchanged explicit photos, including one of an erect penis that he sent to an underage woman.
Defense: He's deaf in his right ear
The defense brought up this point several times, perhaps to justify why Harris did not hear his son's movement in the car.
"I always have to go to the other side of his head to talk to him," his friend, Winston Milling, testified.
Friends speak highly of him
Penny Harrison, a pastor at Harris' church, said she has known him and his wife, Leanna, for two years.
"I knew him to be at typical, loving father of a toddler," Harrison said when the defense called her to the witness stand.
Milling, who had lunch with Harris on the day his son died, said everything appeared normal.
"He loved showing Cooper off to everybody. He liked picking him up, bringing him around. He was always happy. Cooper was always smiling," Milling said.
James Alex Hall went to college with Harris and also had lunch with him on the day his son died. When asked how Harris was acting, he said nothing seemed out of place.
"I'd say normal as you can be," he said. "Nothing stuck out, nothing was weird."
He had movie plans that day
The day his son died, Harris was planning to see "22 Jump Street" with friends after work, according to Stoddard.
Detective: He swore at police officers at the scene
Harris never called 911 and said "f*** you" to a police officer on the scene who asked him to get off his phone, the detective said.
Stoddard said that Harris told police he couldn't reach anyone on his telephone, but phone records show he made three calls after he discovered his son's body, and one between him and his employer lasted six minutes.
Defense believes he was forgetful
Defense attorney Maddox Kilgore said it's not unusual for people to forget children in cars.
"It's easy to get distracted when you get behind the wheel. Everyone's done it. His mind is already skipping ahead to the rest of the day," Kilgore said.
"The results of that forgetting ... were absolutely catastrophic," he said. "But an accident doesn't become a crime because the results were catastrophic."
Investigator: Couple had financial, intimacy issues
Harris and his wife had $2,000 and $25,000 life insurance policies on their son, according to the investigator. He also said Harris' wife "was complaining about (her husband's) sporadic purchasing or overcharging credit cards."
Harris' wife told police the pair were having intimacy issues, according to Stoddard. Texts indicate that she knew he was cheating on her, he said.
In warrants obtained by CNN on Friday, police said Harris discussed with family members the procedure for cashing a life insurance policy, but there is no other information or time element.
"Through the investigation Harris has made comments to family members regarding a life insurance policy that he has on Cooper and what they need to do in order to file for it," the warrants say.
His Internet searches are a focus of case
Harris accessed sites about "people who die," which showed videos of suicides, executions, war, etc., police said. He also visited a site on life without a child and did searches on surviving prison and on "age of consent for Georgia," they said.
"We've only scratched the surface," Stoddard said of the searches.
His activities on day of son's death questioned
The day Cooper died, the father and son stopped at Chick-fil-A for breakfast before he drove the 0.6 miles to work. The breakfast was not out of the ordinary for them.
"Justin stated that this happens two or three times a month. It's daddy-son time, a special occasion to them," Stoddard said.
When he arrived at work, surveillance footage shows Harris backed up his car, according to Stoddard. He said Harris didn't have a backup camera and would have had to turn around or use his rearview and side mirrors. Investigators used a mannequin in the car seat and found the boy's head would have been visible over the top of the car seat.
Harris told police he was supposed to drive his son to day care June 18 but went to work without realizing Cooper was in a car seat in the back.
When Stoddard told him they were charging him, Harris allegedly responded by saying, "But there's no malicious intent."
Detective: His statements were 'all about him'
Harris became emotional when his wife arrived at the police station, according to the prosecution.
"It was all about him: 'I can't believe this is happening to me. Why am I being punished for this?' It was all very one-sided," Stoddard said. "He talked about losing his job. ... 'What are we going to do? I'll be charged with a felony.' "
Leanna Harris later asked her husband, "Did you say too much?" he said.
He has worked for Home Depot for two years
Harris, 33, a Web developer, has worked at Home Depot for two years, according to the Atlanta-based home improvement company.
Home Depot placed him on unpaid leave after the charges were filed.
Stoddard said Harris would take Cooper to day care in the mornings. The couple would split picking the boy up in the afternoons. When Leanna Harris went to pick up Cooper from day care that day, the center told her he was never dropped off. On her way out, she told witnesses: "Ross must have left him in the car. ... There's no other explanation. Ross must have left him in the car," Stoddard said.
He once lived in Alabama
Harris worked at the University of Alabama as a parking monitor and later as a mail delivery clerk between 2001 and 2006, the university said.
Afterward, he was a police dispatcher in Tuscaloosa, Alabama, until 2009, according to Tuscaloosa police spokesman Sgt. Brent Blankley. The department only confirmed his tenure, not details on his work history.
Three years later, Harris graduated from the University of Alabama with a bachelor's degree in commerce and business administration. From there, he went to Home Depot.