When Sen. Bob Menendez was charged last year with participating in a complex bribery scheme, news headlines highlighted a peculiar detail: Investigators had discovered more than $480,000 in cash and 13 bars of gold during a June 22 search of his house in New Jersey.

Days later, the senator offered an explanation for the cash, saying he routinely withdrew large sums of money from his savings account, a custom he said he had learned from his Cuban immigrant parents.

Now, Menendez’s lawyers have gone further, asserting that the habit was rooted in deep psychological trauma tied to his father’s suicide nearly 50 years ago and a family history of confiscated property in Cuba.

They want a psychiatrist who has evaluated Menendez, 70, to testify at the senator’s federal corruption trial about what they have described as “traumatic experiences in his past associated with cash and finances.”

In a newly disclosed letter, his lawyers link the father’s death to a decision by Menendez that, according to the psychiatrist, caused him lifelong trauma — and they want a jury to hear about it.

The psychiatrist, Karen B. Rosenbaum, would be expected to testify that Menendez “experienced trauma when his father, a compulsive gambler, died by suicide after Sen. Menendez eventually decided to discontinue paying off his father’s gambling debts,” the senator’s lawyers said last month in a letter to prosecutors.

On Wednesday, the government made it clear it objected to the doctor’s proposed testimony.

The U.S. Attorney’s Office for the Southern District of New York included a copy of the letter in a legal filing that asked the judge to preclude Rosenbaum from taking the witness stand. The prosecutors are challenging the scientific basis for the psychiatrist’s conclusions and suggesting the defense is trying to evoke sympathy from jurors.

The dispute comes less than two weeks before the start of Menendez’s widely anticipated trial in Manhattan, and offers yet another peek into the senator’s potential defense strategy. The lawyers had previously indicated that he was poised to blame his wife, Nadine Menendez, for at least part of the bribery scheme.

Menendez’s father’s death and his family’s history in Cuba left him with a “fear of scarcity” that led to a “long-standing coping mechanism of routinely withdrawing and storing cash in his home,” the senator’s lawyers, Adam Fee and Avi Weitzman, wrote, summarizing Rosenbaum’s conclusions.

The prosecutors, in asking the judge, Sidney H. Stein of U.S. District Court, to bar the testimony, said Rosenbaum’s opinion “does not appear to be the product of any reliable scientific principle or method.”

They also argued that having the psychiatrist testify appeared to be an “impermissible attempt” by Menendez to make sure that the jury hears about the family history without subjecting himself to cross-examination by testifying.

The prosecutors also called it an improper effort to “engender sympathy based on his family background, in the guise of expert testimony.”

They said that, at a minimum, if Stein were inclined to allow Rosenbaum to testify, the prosecution should be able to have the senator examined by a psychiatrist retained by the government.

Menendez, a Democrat and former chair of the powerful Senate Foreign Relations Committee, is accused of accepting bribes in exchange for his willingness to use his influence to help allies in New Jersey and to aid the governments of Egypt and Qatar.

He will be tried with two New Jersey business owners who also were accused of participating in the bribery conspiracy. Nadine Menendez was charged as well but granted a separate trial, in July, after her lawyers said she had a serious medical condition that would require surgery and an extended period of recovery.

All four defendants have pleaded not guilty.

This dispute over the admissibility of the psychiatrist’s testimony was previewed briefly for the judge in a hearing last week during which Fee outlined the defense’s intentions and a prosecutor vigorously objected.

“Our view at the core is this is just wildly inappropriate as expert testimony,” prosecutor Daniel C. Richenthal told the judge, according to a transcript of the proceeding.

Prosecutors have said that the cash and gold found during the search of Menendez’s house were “fruits” of the bribery scheme.

Richenthal added, “Is essentially an expert allowed to get on the stand and say, ‘I’ve talked to Mr. Menendez’ — who we have no right to call as a witness — ‘He told me X, and I conclude it’s not from bribes.’”

The indictment, which runs 66 pages, outlines a variety of schemes. But perhaps nothing has caught the public eye as much as its descriptions of the cash, gold bars and a Mercedes-Benz convertible found during the search of the senator’s home in Englewood Cliffs, New Jersey.

Investigators discovered much of the cash stuffed into envelopes and hidden in clothing, footwear, a duffel bag and a safe, according to legal filings.

After being charged in September, Robert Menendez offered what he called an “old-fashioned” explanation for at least some of the cash discovered during the search. He said that for 30 years he had withdrawn money each week from his savings account for “emergencies.”

He told reporters that he did this “because of the history of my family facing confiscation in Cuba.”

Prosecutors, however, have said that some of the cash discovered in the house was wrapped in bands showing it had been withdrawn, at least $10,000 at a time, from a bank where neither Menendez nor his wife had an account. This was an indication “that the money had been provided to them by another person,” they wrote in court papers.

Menendez was born in New York City in 1954 to parents who had fled Cuba in the years before Fidel Castro seized control of the country. He has talked and written about growing up in a tenement apartment in Union City, a densely packed community in northern New Jersey that became a magnet for refugees of the Cuban diaspora.

His mother was a seamstress, and his father, a carpenter, died when Menendez was 23, he told The New York Times in 2005.

Rosenbaum, a forensic psychiatrist based in Manhattan, has testified in other high-profile criminal cases in New York. Reports filed with the IRS indicated that Menendez had used his legal defense fund to pay Rosenbaum $4,200 in late March.

This article originally appeared in The New York Times.