If the United States proves the claims, the defendants may give up $50 million in profits that were believed to be made as a result of the manipulation and also pay a penalty of up to $150 million.

The commodities agency says the case involves a complex scheme that relied on the close relationship between physical oil prices and the prices of financial futures, which move in parallel.

In a matter of a few weeks in January 2008, the defendants built up large positions in the oil futures market on exchanges in New York and London, according to the suit, filed in the Federal Court in the Southern District of New York.

At the same time, they bought millions of barrels of physical crude oil at Cushing, Okla., one of the main delivery sites for West Texas Intermediate, the benchmark for American oil, the suit says. They bought the oil even though they had no commercial need for it, giving the market the impression of a shortage, the complaint says.

At one point they had such a dominant position that they owned about 4.6 million barrels of crude oil, estimating that this represented two-thirds of the seven million barrels of excess oil then available at Cushing, according to lawsuits.

This type of oil is also the main driver of prices of the futures contracts, and their actions caused futures prices to rise, the authorities say. “They wanted to lull market participants into believing that supply would remain tight,” the agency said. “They knew that as long as the market believed that supply was tight and getting even tighter, there would be upward pressure on the prices of W.T.I. for February delivery relative to March delivery, which was their goal.”

The traders in mid-January cashed out their futures position, and then a few days later began to bet on a decline in oil futures, with Mr. Wildgoose remarking in an e-mail about the “inevitable puking” of their position on an unsuspecting market, the federal lawsuit says.

In one day, Jan. 25, they then dumped most of their holdings of West Texas Intermediate oil, and profited by the drop in futures.

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The CFTC complaint alleges that between January 8 and January 18 of 2008, oil traders Nicholas Wildgoose and James Dyer entered into forward contracts to buy 4.6 million barrels of oil for physical delivery in February, an amount that represented 66% of their beginning-of-month estimate of the total physical Cushing market. Between January 3 and January 16, the pair is alleged to have also bought about 13,600 February futures contracts (equivalent to 13.6 million barrels of oil) and sold the same number of March futures contracts. The claim is that by creating the appearance of temporarily tighter conditions in the physical market, the February futures price would rise relative to the March and the traders would profit as they closed out their futures positions between January 16 and January 22.

The graph below plots the prices of the February and March NYMEX futures contracts during the month of January 2008. Note that the CFTC is not alleging that these actions were a cause of rising oil prices-- in fact, the price of oil was falling during this period. Rather, the allegation is that these actions resulted in an increase in the spread between the February and March futures price, that is, in the absence of these actions, the February price would have fallen more and the March price would have fallen less.

The CFTC complaint alleges that Wildgoose and Dyer subsequently acquired by January 25 a net short position in March futures and long position in April futures equivalent to 12.2 million barrels. The allegation is that this was done in anticipation of suddenly selling off on the last possible day (Jan 25) all 4.6 million barrels of the physical oil previously accumulated; I gather that the allegation is that this was achieved by finding somebody currently holding rights to delivery of an equivalent volume in March who was willing to swap and take delivery instead in February, provided that the offered February price was sufficiently low. The effect of such a huge last-day sale would have been to depress the February physical price as the market discovered that the apparent big demand for oil just wasn't there. Although Wildgoose and Dyer would of course have taken a big loss on their physical contracts (by virtue of having bought at the artificially higher prices that their bids created and then selling at the artificially lower prices that their sales induced), the CFTC alleges that they more than made up for these losses with bigger profits on the corresponding futures transactions. The CFTC complaint alleges that the pair lost $15 million on the physical transactions but gained $50 million on futures transactions, profiting first by the increase in the February-March spread induced by creating the impression of an unusually tight February physical market, and then later profiting by the decrease in the March-April spread by surprising the market with much more physical oil available for delivery than people had been assuming.

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