In jail accused of killing his 22-month-old son, American Ross Harris told family members how to collect the $US27,000 ($A29,213) life insurance policies on the boy, according to search warrants.

“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,” according to documents obtained by The Atlanta Journal-Constitution.

Ross Harris, who has been denied bond for murder and child cruelty charges, said he accidentally left his son Cooper strapped in his car seat on June 18 while he was at work.

When he finished work more than seven hours later, Harris said he realised his son had been left in the back seat and pulled into a shopping centre parking lot.

Additional search warrants released on Friday gave details of the investigation into Cooper’s death.

During a court hearing, a detective said Harris and his wife, Leanna, had two life insurance policies for their son, one for $US25,000 and the other for $US2000.

Information on whether the family has attempted to claim the money on the policies has not been released.

A spokeswoman for Harris’s employer, Home Depot, previously said a company-sponsored grant was provided to the family to cover funeral costs.

The Harrises told police that their worst fear was that their son would be left inside a hot vehicle.

Cooper was likely to have been dead for more than four hours, according to Detective Phil Stoddard’s testimony on Thursday.

The smell inside the small SUV was overwhelming an hour after Harris pulled the boy out of his car seat, Stoddard said.

Witnesses saw Harris talking on his mobile phone with his dead son beside him on the pavement.

He did not call 911, but a witness did, Stoddard said.

Harris was taken to police headquarters where both he and his wife were questioned, police said.

“During the interview Harris stated that leaving his son in a hot car was his biggest fear,” the search warrants state.

“According to Harris he recently viewed a television show concerning child deaths in cars.”

Leanna Harris was also questioned.

“During the interview with Leanna she also made a similar statement that this was her worst fear,” search warrants state.

“Leanna stated specifically that her fear was that her child would be left in a hot vehicle, not the fear of losing a child.”

Investigators have 10 days to conduct searches and return application documents to the Magistrate Court.