A landmark court hearing involving Crown Casino and poker machine manufacturer Aristocrat has been told that pokies have been deceptively designed to give players the impression they have won when they have not.

Law firm Maurice Blackburn has brought the case in the Federal Court on behalf of Shonica Guy, whose gambling addiction lasted 14 years.

"This case isn't just about me, I want this to stop happening to other people," Ms Guy said.

"For too long now we've been told that it's our fault and we are the only ones to blame for pokies addiction.

"I want this case to show that the machines are misleading and the industry knows that their machines are addictive and they are designed to get us hooked."

Ms Guy is arguing that the reels, symbols and other design features of Aristocrat's Dolphin Treasure machine misrepresent the true chances of winning.

Maurice Blackburn is alleging poker machine manufacturers are engaging in deceptive conduct. ( Photo: Giulio Saggin, ABC News. )

Crown operates 38 Dolphin Treasure machines.

Peter Gray QC took Justice Debbie Mortimer through a simulated play of the Dolphin Treasure machine showing the various line plays, noises and visual displays.

"You'll have to bear with me — I know absolutely nothing about how poker machines work," Justice Mortimer told the court.

He told Justice Mortimer that Crown and Aristocrat had contravened laws preventing misleading and deceptive conduct.

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"The inner workings [of the machines] may not be known to Crown … it's enough that Crown has detailed knowledge of them," he said.

"It has a familiarity with the way these machines appear to the public."

Aristrocrat was "kept informed of the performance of the machines" and has an "ongoing involvement with Crown", he said.

Industry defends 'integrity of products'

Ron Merkel QC, representing Ms Guy, told the court there was a "very close working relationship" between Crown and Aristocrat.

He said that more than 1,000 of the 2,600 poker machines on the floor of the Melbourne casino were made and designed by Aristocrat.

Neil Young QC for Crown said the company was regulated by the Victorian Commission for Gambling and Liquor Regulation — including for the software of the Dolphin Treasure machines and player display information.

He said there was no close relationship with Aristocrat and Crown had "no access" or "knowledge of the inner workings" of the machines and "no access to the software".

Crown is in no "position to modify it or make changes to its presentation", he told the court.

Outside court, Gaming Technologies Association CEO Ross Ferrar said the industry stood by the "integrity of its products".

"They are legislated and regulated heavily, they comply with national standards, they're monitored in the field to make sure they continue to comply," he said.

According to the Department of Social Services (DSS), Australians spent more than $19 billion on gambling in 2014-15, with $13 billion of that spent on pokies.

One in six people who regularly play poker machines has a severe gambling problem, according to DSS statistics.

But Mr Ferrar defended the industry, saying that it complied with regulations, including consumer protection measures and providing adequate information for players to make informed decisions.

"For decades the industry has worked with venues, government and communities to implement measures that you won't see outside of Australia," he said.

Supporters of the legal action gathered outside the court. ( ABC News: Karen Percy )

Pokies info should 'fairly represent' odds

Maurice Blackburn's head of social justice, Jennifer Kanis, said Ms Guy was not seeking damages from the industry, but rather wanted to shine a light on the industry's practices.

"Firstly, what you see is not what you get when you play a poker machine. You see five reels spinning, you think that they are all the same size, but in fact the fifth reel is much larger than the first four. This dramatically decreases your chances of winning," Ms Kanis said.

"Secondly, it appears that the symbols are evenly distributed on the reels as they spin. In fact, those symbols are not evenly distributed."

Mr Gray told the court that claims by Crown that gamblers can expect a return of 87 per cent of their wager is misleading.

Australian Baptist minister Tim Costello was among a number of anti-gambling campaigners outside the court. ( AAP: Joe Castro )

He said the figures were calculated over the course of more than 35 million spins of poker machines and did not accurately reflect a session of play by an individual gambler.

"It's very risky and very dangerous for gamblers to think it's not really too bad if I come away with 87 per cent," he said.

"The house is always winning in the very long run.

"That 87 per cent is returned [to gamblers] in a highly theoretical sense."

Ms Kanis said poker machines were designed to give the feeling of a win, even when a player was losing money.

"You might bet $10 on a spin and get a return of $2, you get the lights and sounds of a win, when in fact you've lost $8," she said.

Maurice Blackburn, which is acting pro bono, said it was not bringing the case in the hope that poker machines would be banned, but wanted poker machines on the market to offer "fair representation" of a player's chances of winning.

"Our view that this case will have ramifications across the industry and across other machines."

Aristocrat and Crown deny the allegations.

The trial is set down for three weeks.