Whistleblower jailed for almost six years after leaking files to the ABC over alleged Afghanistan war crimes

A man who leaked classified military documents that revealed allegations Australian soldiers committed war crimes in Afghanistan will spend at least two years and three months behind bars. 

David McBride, 60, has been sentenced to nearly six-years imprisonment after he pleaded guilty to leaking classified documents that revealed alleged war crimes.

Justice David Mossop sentenced McBride to an aggregated five years and eight months in prison for three charges in the ACT Supreme Court on Tuesday.

The former military lawyer will have a non-parole period of 27 months, meaning he'll remain behind bars until at least August 2026. 

McBride took 235 documents, with 207 classified as secret, by printing them at different defence facilities and taking them out in his backpack.

The classification indicates its disclosure could seriously damage the national interest or people, including the loss of life.

The leaked documents led to reports about Australian special forces soldiers committing alleged war crimes.

An inquiry later found credible information about 23 incidents of potential war crimes, which involved the killing of 39 Afghans between 2005 and 2016.

Human rights lawyers and advocates argued punishing whistleblowers would have a chilling effect on free speech and scare people away from exposing wrongdoing.

In court on Tuesday, Justice Mossop said McBride's actions were a 'gross breach of trust' of his position as a lawyer. 

There was a significant need to deter similar actions in the future but McBride's mental deterioration from a prison sentence also needed to be considered, the justice said.

But he accepted McBride was of good character following numerous character references and a report by a clinical psychologist outlining his morality and sense of justice.

McBride believed soldiers were being unduly investigated for the war crime of murder for actions that didn't reach that threshold because of political interference to show the public the defence force was taking the incidents seriously.

Justice Mossop found he didn't act for financial gain or to help any adversaries.

But he didn't accept McBride's assertion he thought he wasn't committing a criminal offence after the former military lawyer said he believed he would ultimately be vindicated by a court for acting in the public interest.

McBride made 'vague and unparticularised claims' about criminal behaviour by top defence brass, the justice said.

But he accepted poor mental health impacted by depression and PTSD which was self-medicated by alcohol and substance abuse 'made a material, if only minor, contribution... to offending'. 

Speaking to his supporters outside court ahead of his sentencing, McBride said he had never been prouder to be an Australian.

He maintained he did his duty by exposing wrongdoing.

'I did not break my oath to the people of Australia and the soldiers that keep us safe,' he said.

The prosecution had pushed for the former military lawyer to spend a minimum of two years behind bars to reflect the severity of his crime but his lawyers argued for leniency, saying what he did was in the public interest.