A police officer working on a covert drugs operation was told by a target it was easy to spot undercover cops because they never change their shoes.
The undercover officer, using the assumed name Mark Peters, was posing as a businessman planning to open a hydroponics supply shop called The Green Room.
Mr Peters told the Auckland District Court he worked on Operation Lime, an undercover operation that targeted the hydroponics company Switched on Gardener, its parent companies and staff.
The company's owner - Michael Maurice Quinlan - is alleged to have been at the head of what the Crown describes as a "one-stop shop" for cannabis growing equipment.
He and his co-defendants, general manager Peter John Bennett, business development manager Ricky Cochrane, distribution manager Andrew Barry Mai and South Island manager Paul Kenneth Barlow, are accused of belonging to an organised criminal group and supplying equipment used to grow cannabis.
They have pleaded not guilty.
Mr Peters said he met Cochrane to talk about stocking the company's products in the South Island shop.
He was introduced to John Feenstra, sales manager of a related company called Headquarters. Mr Peters told the court that Mr Feenstra said: "You can tell when an undercover policeman comes in because they do one big mistake."
Mr Peters asked what that mistake was.
Mr Feenstra responded: "They don't change their shoes."