David Eastman had sought at least Aus$18 million in compensation. (Representational)

An Australian economist who wrongfully spent nearly two decades in prison for the assassination of a high-ranking police officer was awarded more than Aus$7 million (US$4.75 million) in compensation on Monday.

Former public servant David Eastman was convicted in 1995 of killing Australian Federal Police officer Colin Winchester and sentenced to life imprisonment.

Mr Eastman, who had always maintained his innocence and mounted several appeals, was freed in 2014 after his conviction was quashed.

The Australian Capital Territory (ACT) Supreme Court ordered the jurisdiction's government to pay him just over Aus$7 million.

Mr Eastman had sought at least Aus$18 million in compensation.

The 74-year-old told the court that not only had he lost the opportunity to have a family and pursue his career, his mother and sisters died while he was behind bars.

The court also heard that he witnessed a murder during his incarceration and still suffers vision impairment in one eye after he was assaulted by another prisoner in 2006.

Lawyer Sam Tierney told reporters outside the court in Canberra that his client was "very happy" with the decision.

"He's lost a significant chunk of his life and he's obviously got some thoughts in mind as to what he might do with (the money)," he said.

It was unclear whether the ACT government would appeal the decision. The case had already cost the territory more than Aus$30 million, according to public broadcaster ABC.

Mr Winchester was shot dead while getting out of his car near his home in suburban Canberra in 1989. No one has been held accountable for the murder.