Ewen Macdonald was the one on trial but it was his lawyer who stole the show at the High Court as he delivered the closing address that would destroy the prosecution.
Mr King's speech was intense and almost theatrical at times.
His delivery gripped the nation as he picked apart the police case against his client, imploring the jury to return a not-guilty verdict.
"When you take a step back, divorce it from the emotion, the sympathy, and when you look at cold, hard evidence - not allegation - then every strand of the Crown case failed," he said.
Yesterday, that is exactly what the jury did.
And the acquittal of Ewen Macdonald for the murder of his brother-in-law Scott Guy can be added to Mr King's lengthy list of successful defence cases.
Mr King was educated at Tongariro High School, Turangi, and the University of Otago. He was admitted to the bar in Dunedin in 1993 and worked for three years as junior counsel to Judith Ablett-Kerr QC. He has been counsel in more than 350 jury trials. Of those, about 50 have been homicide cases.
He has defended some of the New Zealand's most high-profile killers, and been successful in getting acquittals for others facing murder charges.
In 2009, Mr King was on the defence team for Clayton Weatherston, who was found guilty of murdering former girlfriend Sophie Elliott.
On his website, Mr King described Weatherston's trial as "undoubtedly one of the most unpopular trials of modern times".
In 2008, he represented Daniel Moore, who was convicted at trial of the murder of Tony Stanlake, whose handless corpse was found washed up on a Wellington beach.
Mr King also hit the headlines for his work on the case of John Barlow, who was tried three times and convicted for the murders of Wellington businessmen Gene and Eugene Thomas.
He was unsuccessful in an appeal against that conviction to the Privy Council but continues to work on the case.
Mr King is no stranger to the television screen. He was the host of TVNZ7's The Court Report, taking the public behind the scenes and explaining legal issues and cases in-depth.
Away from the robes and ceremony of the courtroom, Mr King's main focus is his family, who live with him in Lower Hutt.
"Greg has been actively landscaping the property over the last 10 years. The family share their home with four "rescued" cats, four chickens and a Scottish terrier named Holly," his website says.
"Greg is also an avid sports fan. He has previously coached boxing, including training All Black legend Bernie Fraser for the 2002 Fight for Life. Greg is a former president of the Otago Boxing Association. Other favoured sports include rugby union, rugby league, cricket and netball."
- Anna Leask.
