ASIC is asking a Federal Court judge to reject much of the evidence of a senior executive from Westpac's treasury in a civil case centred on alleged misconduct in the bank bill market six years ago.Closing submissions are underway in the sixth week of hearings in Melbourne before Justice Jonathan Beach."You're asking me to make a strong adverse credit finding against Colin Roden, aren't you?" Justice Beach asked ASIC counsel Philip Crutchfield early yesterday.Roden, Crutchfield said, "tried to reconstruct a purpose because he can't remember the purpose on particular trading days because, of course, he's denying [a] case of some systemic trading rate practice."We say the way in which [Roden] tried to explain away some of the emails, just defied credulity and he got in the witness box and gave those explanations. So it follows we are asking your Honour to reject his evidence, yes."Beach continued to probe, asking if "then I must find that against Sophie Johnston as well, that she was somehow falsely denying this rate set charging practice and giving questionable evidence about her conversations with Mr Roden and others?""We do say that," Crutchfield said, "and it's a long time ago, and the hedging narrative is a half-truth."Crutchfield argued later that "It's commonsense, we say, if everybody else is doing it. It's a bit like the Tour de France, if you're going to compete, you're going to do it, too."And if you're not going to do it, too, you would write a memo, [but] that's not the Westpac way."Justice Beach put a glossy view of the conduct of Westpac's rate traders to ASIC."You've got these traders, they're highly skilled, they have many competingstrategies, some of which are in tension with each other but … they've got all sorts of purposes and influences," Beach said. "They have to be opportunistic, they have to be flexible, they have to be smart. And they're turning up on particular days trading in bills, yet you [ASIC] want to craft a lawyer's construct of some formalistic practice over two years and I've just got a problem conceptually."Crutchfield went on to tell the court, "There's lots of missing pieces of the puzzle, and we say that having regard to that, Westpac might have engaged in that practice throughout the relevant period [2010 to 2012] because here's all the occasions they did on the evidence that we had." "Every time you see the deliberate building up of very large rate set exposures - and your Honour saw the evidence of Mr Roden and [Westpac group treasurer Curt] Zuber about the basis swaps and how it swaps from the 90 day bills into the 30 day, the interest rate risk gets swapped into the 30. "You're building up these massive rate set exposures, and that looks suspicious in and of itself …. The reason it looks suspicious is it's sort of like driving a Ferrari and slamming on the brakes every time you get to the corner. "It's a very dangerous way to drive, which