In 1989, on a hot January night in Canberra Australian Federal Police Assistant Commissioner Colin Winchester was parking his car near his house.

Moments later, he was shot dead.

Colin Winchester was the most senior police officer ever murdered in Australia.

Four years later, an ex-Treasury official famous for feuding with dozens of Canberra locals was charged with his murder.

David Eastman had grown up as a the son of a diplomat, and at high school he became the dux of Canberra Grammar.

But after he joined the public service, things went badly wrong.

Eastman became well known for conducting public feuds with various high-profile figures in Canberra, and he was granted medical invalidity from his job in the Treasury, which he fought for many years to have overturned.

One of the people Eastman had made death threats against was Assistant Commissioner Winchester.

Eventually after an intensive surveillance operation, Eastman was charged, and found guilty of murdering Colin Winchester.

He spent 19 years in prison. But in 2014, after new evidence emerged, he was granted a retrial.

Journalist Sam Vincent spent five months at David Eastman's retrial in 2018, and saw him walk out of court a free man.

He says there are still persistent questions about who killed Colin Winchester.

Further information

Sam Vincent's essay A Nagging Doubt was published in the December 2018 issue of The Monthly