It's a stance that has infuriated the New Zealand Rugby Union who have been careful in all of their public comments to not make allegations of blame or insinuate or speculate who might have planted the device.
But following the Wallabies 37-12 defeat at Eden Park last year - their fourth consecutive loss to the All Blacks - Cheika launched into an extraordinary tirade.
"I would say they caught me a bit offside with the accusation that we tried to bug them," said Cheika when he was asked whether his and the Wallabies' relationship had turned septic with the All Blacks.
"Really? Hello? Honestly? They had that the whole week..? That showed a lack of respect. I wouldn't be smart enough to get that sort of stuff organised. I am too busy working on my own thing."
The sense of injustice and resentment simmering within the Wallaby camp didn't reside that night at Eden Park and Hansen confirmed that Cheika sought him out in May when the two men were in Tokyo to see the draw being made for the 2019 World Cup.
"I don't know if he confronted me," said Hansen. "We had a chat in Japan and I made it clear to him that we didn't highlight [the Wallabies as a guilty party]. I said to him there are only x amount of people who would take that opportunity [to plant a bug] and whether we would like it or not, if you [Cheika] found a bug in your [Wallabies] team room, we [All Blacks] would be one of those. So we haven't named them as that and we never will because we don't know who put it there.
"I don't know where they feel the inference was because we haven't said it. We don't know who put it there and we said at the time and that hasn't changed. We can't help how they feel."
An already difficult and tense relationship between the two sides now sits on the cusp of yet more ill-will and bad blood developing, depending on the verdict in the Gard case.
A guilty verdict will incense the All Blacks while exoneration will effectively leave the mystery unsolved and the Australians thinking the cloud of suspicion they believe is hovering for them, lingering for longer.
Hansen said that he was keeping an eye on the ongoing Gard case. "Obviously we are watching with interest. He is a good man and we feel for him."