Nicolo Milioto, a key witness at Quebec's corruption probe, was incapable of explaining what the Mafia did or what the Cosa Nostra was. But he was sure of one thing: He had heard of Omertá, the Mob's traditional code of silence.

"It means that you don't talk," said the 64-year-old retiree, described as a pivotal figure in the scheme that robbed taxpayers of millions by upping public-works contracts.

A reluctance to talk marked Mr. Milioto's appareance before the Charbonneau Commission on Tuesday, as he displayed a fuzzy memory and evasive answers when it came to his frequent cash exchanges with Nicolo Rizzuto Sr., the late Mafia chieftain.

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Mr. Milioto, a retired construction boss known as Mr. Sidewalk, was caught numerous times on police surveillance camera stuffing cash into his sock at the Rizzuto crime family headquarters known as the Consenza Social Club, at times sharing a table with Mr. Rizzuto and dividing wads of bills into piles.

The series of secret tapes, shown before the Charbonneau Commission, make one thing clear: Cash, lots of it, stacked in brick-thick piles and counted by hand, pulled out magically from paper bags and stuffed into socks and pockets, flowed in abundance at the Mob gathering spot.

Mr. Milioto says he acted as a humble conduit, delivering cash to Mr. Rizzuto mainly from former construction entrepreneur Lino Zambito, as a favour.

He denied he was collecting a 2.5-per-cent cut from construction bosses and delivering it to the Mob, a scheme described by prior witnesses; the money handed to Mr. Milioto also allegedly served to fund former mayor Gérald Tremblay's municipal party, Union Montréal.

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In an emotional turn, Mr. Milioto denied before the commission that he was a member of organized crime, saying today he regrets what he did.

"It was maybe the error of my life … I lacked judgement," he said.

Mr. Milioto's apparent loyalty to his acolytes highlights the challenges facing the commission as it attempts to penetrate the shadows of a murky system that allowed entrepreneurs to collude and inflate construction contracts in Montreal.

Over and over, Mr. Milioto displayed a shaky memory of events or cast himself as a friendly service-provider, and said he considered handing Mr. Rizzuto wads of cash in the backroom of a café "banal." At one point, he said he had simply been a hard-working businessman, toiling up to 70 hours a week, providing for his family and putting his five children through school.

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Still, Mr. Milioto admitted that he had paid a visit to the slain Mr. Rizzuto's home, and had borrowed $20,000 from him even though Mr. Milioto ran a multimillion-dollar construction business specializing in sidewalks. He said he didn't use a bank because Mr. Rizzuto's loan was interest-free.

Mr. Milioto was initially elusive in his answers, at times facing commission counsel Sonia Lebel with his chin up and his head high. He became somewhat less defiant after Justice France Charbonneau cautioned him that giving vague answers could constitute contempt of court.

He said he knew about the Mafia from newspapers and TV, and didn't know exactly what the organization did. He was, however, willing to share his personal credo.

"If you respect me, I'll respect you," Mr. Milioto said. "If you mistreat me, I can mistreat you the same way."