It was a family affair at Sydney's harness racing corruption trial: the champion driver Greg Bennett, accused of bribing a steward; his dad, Jim, the trainer with 50 years in the game; and the driver's brother-in-law, a retired school teacher who crunched the statistics to show Bennett drove plenty of winners for other trainers.

All three gave evidence in Sydney District Court yesterday when Jim Bennett denied he had ever given his horses a "milkshake" (sodium bicarbonate) or "bute" (phenylbutazone) or ever used tubing to deliver such illegal substances to their stomachs to boost their performance.

Jim Bennett also denied placing bets so he and his son could divide the winnings in a three-way split with a corrupt steward, Matthew Bentley.

Greg Bennett pleaded not guilty to six counts of giving or offering bribes to Bentley, who turned Crown witness after he struck a deal for indemnity from prosecution.

The driver says Bentley is lying and that he never made any payments, which the steward alleges ranged from $200 to $1000 over six race meetings.

Guy Newton, for the Crown, took Greg Bennett through secret police tapes of his phone conversations with horse owners and trainers who did business with his father's stable in 2010 and 2011.

In one call, there is reference to a horse caught with "higher bicarb" at a race meeting.

That horse was linked not to the Bennett stable but to a female trainer from Perth.

"Oh-oh-oh," Bennett said on one of the tapes, which the jury has heard.

"Yeah," came the reply.

"Oh shit!" said Bennett.

Mr Newton asked what this conveyed. "Well, it was bad luck for her," the driver replied.

Greg Bennett said he never told his father or anyone else about the friendship he formed with Bentley and their many phone conversations, including on race days. Did he agree that colleagues would have "frowned upon" such contact?

"Well, maybe, yes," he said, but denied he had a deal with Bentley not to swab horses that he drove.

Mr Newton sought to demonstrate that Greg Bennett had an active business as a trainer in his father's stable at Kanahooka Lodge, south of Wollongong.

The barrister quoted an intercepted call between Greg and Jim Bennett, in which the son gave his father instructions - "you'd better tell Paul to tell Noel to tell Michael" - about the horse My Bravado.

"Is that you telling your father what to do?' Does it mean you were top of the tree?" Mr Newton asked.

"No," Greg Bennett replied. He denied he was a joint owner of horses, although he did do trackwork for his father and he played a role in the buying and selling of horses.

"I've never hid the fact that I go down and help my father," Greg Bennett said.

"There's no doubt about that," Jim Bennett said, when asked if he had the final say.

His daughter's husband, Doug Robinson, told the court he had used the computer in his bedroom to go through Harness Racing NSW records to show Greg Bennett's winners for horses trained by his father and for other trainers in the period of the alleged offences.

The trial continues.