Farmer Ian Turnbull will be aged more than 100 when his non-parole period expires for murdering an environmental officer near Moree in 2014.
An elderly farmer who gunned down a diligent NSW environment officer during a protracted and terrifying ordeal has been jailed for at least 24 years.
Ian Turnbull, now 81, used a hunting rifle to murder Glen Turner, 51, who was on public land with a colleague on July 29, 2014, near the farmer's property at Croppa Creek in the state's north.
In the NSW Supreme Court on Thursday, Justice Peter Johnson jailed him for a maximum of 35 years for the murder and for detaining the colleague for advantage.
The judge said Turnbull had built up a strong resentment, even hatred, for Mr Turner and his employer, the Office of Environment and Heritage, over battles about alleged illegal land clearing.
During the 20 minutes the farmer held both officers at gunpoint, he accused Mr Turner of persecuting the Turnbull family, saying "the only way you are going home is in a body bag".
He shot Mr Turner twice, ignored Robert Strange's pleas to stop, and fired the third and fatal shot as his victim made a desperate dash for safety.
Turnbull was motivated by "retaliation and revenge" said Justice Johnson who rejected a claim that the farmer was now remorseful.
Noting Turnbull was 79 at the time of the murder, the judge said "courts have made it clear, age is not a licence to commit an offence".
The fact that Mr Turner was a public official gunned down in the course of his occupation made the murder particularly serious, he added.
He set a minimum of 22 and a maximum of 32 years for the murder, but increased this to 24 and 35 after adding on a component of the term imposed for the offence relating to Mr Strange.
The judge acknowledged that the term most certainly could be considered a "de facto life sentence" given Turnbull's age, but said the crimes warranted no less of a sentence.