ALEXANDRIA, Va. -- Former U.S. Rep. William Jefferson faces several obstacles to being acquitted of bribery, racketeering and other federal charges -- and topping the list is explaining the $90,000 cash stashed in his freezer. 

Jefferson, a Louisiana Democrat who represented parts of New Orleans until losing his bid for re-election last year, goes on trial Tuesday in U.S. District Court in Alexandria on allegations that he received more than $400,000 in bribes in return for using his influence to broker business deals in Africa. 

Defense attorneys are expected to attack the credibility of a witness who frequently wore a wire for the government. They have to hope a jury will accept a fairly legalistic distinction that Jefferson's conduct wasn't bribery, but was more technically akin to influence peddling. And there's the money in the freezer -- $90,000 wrapped in aluminum foil, found by federal agents in August 2005 in Jefferson's Washington home. 

Just days earlier, agents videotaped him at a northern Virginia hotel accepting a suitcase stuffed with $100,000 cash from a cooperating witness. 

The freezer funds became such a headline that Robert Trout, Jefferson's lawyer, suggested at a recent hearing that potential jurors need to be reminded during the jury selection phase of the trial that the Jefferson case is the one about "the money in the freezer" to try to weed out jurors exposed to pretrial publicity. 

U.S. District Judge T.S. Ellis III agreed the reminder would be appropriate. 

Jefferson himself has said very little about the money. After he was arraigned and pleaded not guilty in June 2007, he said "when all the facts are understood, I trust that I will be vindicated." 

He also emphasized that the $90,000 was "the FBI's money" and given to him as part of their investigation of him. 

The cooperating witness who gave Jefferson the cash was Lori Mody, a northern Virginia business executive whose complaint to the FBI in March 2005 launched the probe against Jefferson. According to the indictment, Mody was becoming suspicious that Jefferson constantly was demanding cash to facilitate various business deals. She is expected to testify against the former congressman. 

Jefferson's lawyers have questioned whether Mody is a reliable witness and whether her memory can be trusted. They have sought records of Mody's mental health history and raised questions about possibly erratic behavior, including Mody's fears that she was being stalked. 

Other allegations raised in court papers by Jefferson's lawyers remain under seal. 

Prosecutors have accused Jefferson of trying to smear and intimidate Mody. They argue that Mody's memory of events is irrelevant when she was wearing a wire and the conversations in question have been recorded. 

Trout has said his client has a constitutional right to confront witnesses, and that not all conversations between the two were recorded. 

Mody's lawyer did not return calls seeking comment. 

The most important question, though, might be a technical one -- the issue of what constitutes bribery under federal law. 

Bribery occurs when an officeholder receives something of value in exchange for an "official act." Defense lawyers argue that unless Jefferson took money in exchange for an official duty like voting on a bill or sponsoring legislation, it isn't illegal. It may be immoral influence peddling, they say -- but not illegal. 

Prosecutors offer a more expansive view: If Jefferson used the influence of his office to benefit constituents, then it falls under the bribery statute. 

George Jackson, a Chicago-based defense attorney with the Bryan Cave firm and a former federal prosecutor with expertise in political corruption cases, said bribery is a difficult crime to prove. No federal law prohibits a congressman, for example, from holding a second job as a business consultant and receiving payment. 

But he said Ellis' pretrial rulings on the issue so far have been favorable to prosecutors. And jurors may be less inclined to distinguish between immoral and illegal. 

The trial is expected to last at least a month.