New Zealand's first insider trading trial has reached a dramatic conclusion - a hung jury.

Twelve of Hamish Marc Sansom's peers were selected to judge the landmark case in the High Court at Auckland over the past two weeks.

Sansom, who worked as a senior manager for Eroad, a transport and technology company, was charged with insider conduct under the Financial Markets Conduct Act.

His was the first criminal trial on such a charge in New Zealand's legal history.

Today, after lengthy deliberations over more than two days, a jury returned to tell Justice Anne Hinton they could not reach a verdict and were subsequently discharged.

The judge had given the jury the option of reaching a majority (11 out of 12 jurors) verdict rather than a unanimous verdict.

However, she did not give what is known to lawyers as the Papadopoulos direction.

A Papadopoulos direction encourages jurors to persevere with their deliberations and to demonstrate a willingness, having listened carefully to the views of other jurors, to change their view.

Sansom, who appeared stoic as the court heard the jury had reached an impasse, will have his case called again next month.

The Financial Markets Authority's (FMA) prosecution of Sansom was based around evidence from a series of texts he exchanged with a former workmate after a tip-off about Eroad's United States sales data in 2015.

The confidential data showed Eroad, a publicly listed Kiwi company - which also operates in Australia and the US - was performing badly as it attempted to break-in to the North American market.

Sansom sold 15,000 of his shares in the company just days after he received the texts.

Honey's September 22, 2015 message to Sansom read: "US sales not doing [too well], time to sell up? Confidential obviously."

It also included a photo of an executive sales summary.

"You're a bad boy, but thanks!" Sansom replied.

But, a minute later Sansom also texted Honey: "Was going to sell down significantly anyway."

The court heard during the trial that Sansom had been on Eroad's executive management team after a lengthy career at Vodafone - where he now works again - and was responsible for a team that included insights and analytics manager Jeffrey Peter Honey.

Sansom hired Honey after the pair grew friendly while working at Vodafone.

FMA prosecutor Nick Williams told the court that Sansom, while not selling all his shares, did dump the 15,000 as a result of Honey's "secret information" and to avoid a personal financial loss.

However, Sansom's counsel David Jones QC argued that his client was simply smarter than everyone else and had analysed market trends.

He told the jury during his closing address that Sansom's case was not the Wolf of Wall Street, referencing infamous American stockmarket manipulator Jordan Belfort.

On September 24, 2015, when Sansom sold the 15,000 Eroad shares he did so at a price of $3.41 each.

Four days passed before news of Eroad's US sales setback went public, crashing its stock price.

"The market reacted badly," Williams said.

The announcement resulted in the biggest daily and weekly fall in Eroad's trading history, since its initial public offering in August 2014.

By October 2, 2015, its shares were trading at $2.60 each - dropping by 21 per cent.

Court documents obtained by the Herald show a day prior Honey had text Sansom stating, "I hope you sold."

Sansom replied: "Yep, I sold as much as I could but still have lots left. Not many buyers out there."

Williams said Sansom had moved the Eroad shares out of his family trust and into his own name before selling them online.

"He had insider information and was prohibited from selling," Williams told the jury, "material information that wasn't generally known and that is a criminal offence."

On November 19, 2015 the FMA received a referral from NZX market surveillance about Sansom's trading.

Jones told the court the Crown was trying to paint his client as a bad man, when really he was a humble father and astute trader.

"This man looked at the reality of publicly available material," he said, adding Sansom already knew Eroad's US sales were well below expectations.

"This man looked at the numbers and he worked it out for himself. He had planned to sell the Eroad shares for months.

"It's not rocket science, it's just being smart and being perceptive," Jones said.

"You can't be penalised for being smarter than someone else for analysing material and this man is an analyst."

Sansom also argued he didn't know the US market setback wasn't public information at the time he dumped his shares.

"For anyone to be guilty of a crime you have to have a guilty mind," Jones said.