The lawyers in the market-manipulation trial of futures trader Donald Wilson Jr. and DRW Investments gave their closing arguments on Wednesday. Only problem was that U.S. District Judge Richard Sullivan repeatedly interrupted the lawyers for the CFTC as they gave their closing arguments, suggesting they had failed to prove a crucial point.

Mr. Wilson and his firm, DRW Investments LLC, are charged with having manipulated an interest-rate contract in 2011 to yield $13 million in profits.

Judge Sullivan questioned whether the agency had successfully proven that DRW’s actions had created an artificial price for the contract, which the CFTC must do to win its case.

“There are multiple elements to market manipulation and it’s not clear to me that you’ve proven a central one, which is artificiality,” Judge Sullivan said in a Manhattan courtroom.

Earlier in the trial, Judge Sullivan grilled Mr. Wilson over evidence in the case, including an email in which a DRW trader described companies that took the opposite side of the firm’s trade as “suckers”.

But on Wednesday the judge’s toughest questions were aimed at the CFTC. He admonished the agency’s lawyers for focusing on what they described as “illegitimate” bids and sidestepping the issue of whether DRW had caused an artificial price.

“You keep using ‘illegitimacy’, which is a very fuzzy term, to somehow be the equivalent of artificiality,” Judge Sullivan said. Arguing that DRW’s bids created an artificial price because they were made with an illicit intent was “so circular as to be nonsensical,” he added.

Background Information.    The CFTC’s allegations against DRW stem from a big trade in interest-rate swap futures that the firm carried out in 2010 and 2011 on an exchange owned by Nasdaq Inc. The contracts allow companies to bet on or protect against swings in rates.DRW bought more than $350 million of the futures in late 2010, expecting the position to rise in value, the CFTC said in its lawsuit. In January 2011, the firm began placing bids in a 15-minute afternoon settlement window used by the exchange to determine the contract’s closing value at the end of the day. The CFTC argues that those bids, which continued through August 2011, were an illegal strategy called “banging the close” that was aimed at enhancing the value of DRW’s large position in the futures contract.