Ian Robert Turnbull, 79, is accused of ambushing and shooting dead Office of Environment and Heritage worker Glen Turner on a dirt road at Croppa Creek, north of Moree, on July 29.

Mr Turnbull, who turns 80 next month, appeared in the NSW Supreme Court in Sydney on Thursday in an unsuccessful attempt to get bail.

His wife of 55 years, Robeena June Turnbull, told the court Mr Turnbull came home to their property and sat in a chair, where he remained for hours until police arrived.

"He just looked wretched ... He was somewhere else," Mrs Turnbull said.

She said  her husband told her: "I simply cracked. I didn't mean to kill him."

Mr Turnbull's barrister, Tony Bellanto, QC, said the family could lodge $300,000 cash and offer security of $1 million or more as a condition of bail.

Mr Bellanto said Mr Turnbull had numerous health problems including peripheral neuropathy which curtails his ability to walk. He also has a pacemaker.

Mrs Turnbull said she was living with her son, Grant, in Brisbane and made a weekly 12-hour round trip by plane to visit her husband at Cessnock Correctional Centre, where he is being held on remand.

She said that if he had been granted bail, the couple would live with a cousin in Castle Cove on Sydney's north shore.

She said her husband had difficulty walking and that she could see he was in pain.

"He said he could only walk about 10 feet and then he would crumple to the floor," Mrs Turnbull said. "But [he only expresses discomfort] when I ask him. He doesn't come out complaining."

Crown prosecutor Todd Alexis, SC, opposed bail.

The hearing continues.

with AAP