Duncan was arrested and charged with possession of pre-cursor materials, and the property was sealed off and remained under a police cordon until it was lifted on September 22.
The Crown alleges Williams, under Duncan's direction, crept across the cordon into the property in the early hours of September 21, 2010, and dug up a bucket containing half a million dollars.
At the hearing Justice Peter Woodhouse was played a series of intercepted telephone calls between Duncan and Williams and their associates during September 21 and 24, 2010.
Crown prosecutor Greg Hollister-Jones said these calls were clear evidence that Williams had crawled "army-style" into the property the morning after the raid and dug up the buried loot.
Later the same day police found a newly dug hole near the crest of some pine trees, he said.
Mr Hollister-Jones pointed to a call between Williams and Duncan's sister during which Williams tells her, "I found mega, but I've recovered a bit."
Duncan is later heard quizzing Williams about the buried "$500k" and Williams tells Duncan, "Yeah mate, I've recovered that bucket and the big lot ... The mega lot is still all there."
Mr Hollister-Jones said on September 24 that Williams told a male associate that he intended to disperse some of the cash to the man and another associate.
He said it was clear Williams dug up the bucket of cash and later lied to Duncan about how much he was able to retrieve.
Lawyers for Williams and Duncan told Justice Woodhouse that the removal of an item from the property was not disputed, but the Crown had failed to prove that the item was $500,000 cash.
Justice Peter Woodhouse reserved his decision.
Both Duncan and his associate Wallace Bramley, 38, from Papamoa, were acquitted at trial last month on charges of manufacturing $2.3 million worth of methamphetamine and conspiring to supply the drug.
But the pair are to be sentenced in February in relation to a raft of other P-manufacture and supply charges. Williams is also awaiting sentencing on a charge of conspiring with Duncan to supply P.