Last fall, Justice Department prosecutors struck out trying to convict three British traders of using an online chatroom to illegally fix prices in the foreign exchange markets. It took a jury just five hours to reject the charges.

Undeterred, the feds are taking another shot in a trial now underway in the Southern District of New York against former JPMorgan Chase & Co. FX trader Akshay Aiyer, represented by Willkie Farr & Gallagher's Joseph Baio, Martin Klotz and Jocelyn Sher.

This time around, the feds have some advantages. 

The trio of Brits who were acquitted were tried together, and the government had just one primary cooperating witness challenging the defendants' version of events. 

By contrast, Aiyer—who faces up to 10 years in prison and a $1 million fine if convicted—stands alone. Two former traders who pleaded guilty are testifying against him in a bid for leniency.

Moreover, the currencies at issue, such as the Russian ruble, the Turkish lira and the South African rand, have smaller markets than the euros-U.S. dollars  traded by Rohan Ramchandani, Christopher Ashton and Richard Usher. That might make it easier for prosecutors to show price fixing.  

But so far, the Willkie team is putting up a strong fight. Consider opening statements on Oct. 31.

The first thing Antitrust Division lawyer Kevin Hart said to the jury, according to a transcript of the proceedings, was "Conspiracies are nice, probably shouldn't put this in a check.'"

Hart continued, "Those were messages exchanged by [Aiyer] and his co-conspirator, just after cheating a customer. Why did they exchange these messages? Because they were in a conspiracy, a conspiracy to fix prices and rig bids."

Sounds damning, right? But it was as though Hart walked into a trap.

In an unconventional move, Sher—who is an associate—was tapped to deliver the defense's opening, and she deftly undercut the prosecution's soundbite.

"[T]he critical evidence in this case will be the text of what Mr. Aiyer and the others said to each other in chatroom conversations," she said. "We submit, however, that the government will focus on fragments of what was said in those chats, highlighting colorful or questionable language…. But we will give you a fuller picture of the trading in this case and the conversations that took place before, during, and after the episodes at issue."

She circled back. "[T]he lines that the government will show you were selected from over 3,000 chats between two or more…chatroom members, which run a total of over 9,000 pages. The government only plans to show you a few dozen of these chats, and only then, selected lines from each."

And then boom, she proved her point with devastating effect. That "conspiracies are nice" quote? 

 "What I want you to focus on is Mr. Aiyer's immediate response," Sher said. "Mr. Aiyer wrote 'Hah, hah, hah.'"

As for the first cooperating witness, former Citigroup trader Christopher Cummins, it's not clear how damaging his testimony will be.

On direct, he dutifully reviewed multiple chat room messages with DOJ's David Chu. Here's a typical exchange.

Q. When Mr. Aiyer says 29.1000, what does that mean?

A. That's the price that he gave to his client.

Q. And was Mr. Aiyer supposed to be giving you this information, the pricing for his client?

A. No.

On cross, Baio stressed that Cummins was testifying in the hopes of getting a lighter sentence and that he was involved in a "separate and apart conspiracy" with other traders for years before he met Aiyer.

And he launched a brutal attack on his honesty in dealing with prosecutors.

Baio said, "When did you form the intent to lie to the government, to evade responsibility under the criminal charge even though the lie created a fresh crime? When did you create that intent?"

Cummins replied, "I didn't go in with the intent. At some point or another, I attempted to evade the questions of the prosecutors."

The exchange continued:

Q. When did you form an intent to lie?

A. It's not like I formed an intent and then lied. If someone asked me a question and I didn't give the full truth, that was essentially the lie. I didn't have a plan in mind.

Q. It was a sort of spontaneous thing?

A. Yes.

Q. And when you lied, you knew that you were lying to the federal government?

A. Yes. Yes.

Q. And you knew that that itself was a crime?

A. Yes.

Q. And how many times did you lie when you met with the federal prosecutors in October of 2014?

A. I don't know.

Q. Well, you've met with the prosecutors how many times?

A. Since that first meeting, we've met 18 times.

Q. And in those 18 times, did you tell them in words of substance, look, I lied, and here's where I lied?

A. I did not.

Q. Well, did you tell them where you shaded the truth or where you didn't tell them the full story?

A. No.

Q. And they didn't ask you?

A. They did not.

Ouch.

The trial before U.S. District Judge John G. Koeltl is slated to run for about another week.