The last time Philippe de Montebello was out of his comfort zone was probably back in his days at a Paris lycee, before moving to the United States at age 13. But the suave, superbly self-confident, recently retired director of the Metropolitan Museum of Art was certainly uncomfortable yesterday while being cross-examined by Fred Hafetz, the lawyer for Anthony Marshall, Brooke Astor’s son.

The prosecution, on whose behalf Mr. de Montebello was called to testify, has been trying to establish that Mrs. Astor was senile by the time she signed codicils to her will, in 2003 and 2004, which transferred to Marshall assets once promised to New York’s major cultural institutions, among them the Met.

Mrs. Astor “mentioned she’d rather have her dogs Boysie and Girlsie there than her son and that bitch,” referring to Charlene.

Mr. de Montebello was only too happy to testify that this was indeed the case. He recalled an April 2004 tea at Mrs. Astor’s Park Avenue apartment with her friend Annette de le Renta. “She was basically looking at me—‘Who are you?’ Looking at Annette—‘Who is this man?’ Over and over again. I’d known her over 30 years.”

A few months earlier, she’d visited his office at the Met and become disoriented, he said, asking “Where exactly am I?”

Was she rational, the prosecutor asked Mr. de Montebello. “No,” the museum director stated flatly.

All of this would have seemed pretty damning to the defense, which is asking the jury to take the rather strenuous leap of faith: They concede that Mrs. Astor suffered from Alzheimer’s disease, but maintain that she had good days and bad days, and it was on the good days that she gladly forked over full control of her fortune to her only son. But alas, there was one small problem for Mr. de Montebello. The defense was able to point out that at approximately the same time that Brooke was supposedly losing it, she was also making generous gifts to the Met—gifts, the defense insinuated, it would have been indecent to accept from an old lady who didn’t know what she was doing.

By accepting a $20,000 porcelain Qing dynasty figure in June 2002 and a generous offer to pay half the $235,000 price of a seated Burmese Buddha in 2003, wasn’t the Met acting as though Mrs. Astor had her wits about her? “You would not have accepted it unless you thought it was a rational act?” Mr. Hafetz asked de Montebello with some incredulity.

What Mr. de Montebello could not say, of course, is that the most important element in any museum director’s job description is not connoisseurship or even the ability to mount blockbuster exhibitions, but the finesse with which they separate wealthy patrons from their Monets and their money.

“I would not have given it a second thought,” Mr. de Montebello replied, perhaps a bit superciliously. “It was such a regular occurrence.”

Earlier in the day, Kevin O’Flaherty, Mrs. Astor’s audiologist—in other words, her hearing-aid specialist—testified both to her severe hearing loss and also to her habit of flirting mercilessly with him and regularly sticking it to Charlene Marshall, her daughter-in-law. In what was destined to become the day’s headline—indeed it was zipping around the Internet before the end of the lunch break—Mr. O’Flaherty testified that in 2000 he innocently asked Mrs. Astor what she was doing for the holidays and “she mentioned she’d rather have her dogs Boysie and Girlsie there than her son and that bitch,” referring to Charlene, though Mr. O’Flaherty diplomatically spelled the word out.

Piling on Charlene seems to be the trial’s leitmotif, and John Dobkin, a friend of Brooke’s who came on before Mr. O’Flaherty, did his part. Recalling a visit to Cove End, Brooke’s Northeast Harbor, Maine, estate, where he testified that while sitting on her porch, Mrs. Astor pointed in the direction of the road and said, “That’s where Charlene would walk back and forth day after day trying to get Tony’s attention.” Charlene, seated in court beside her daughter Inness, stared grimly ahead.

But de Montebello was the day’s big draw, and he gave the jury a lovely window into what life is like at the pinnacle of Manhattan society. He recalled gilded dinner parties at Mrs. Astor’s apartment, where her modus operandi was to turn to a prominent guest such as Kofi Annan and ask him to discourse on his field of expertise.

Mr. Hafetz tried and at least partially succeeded at scraping away some of the museum director’s luster—and certainly his patience—by having him review endless minutes of Met board meetings. The ostensible purpose was to prove that Mrs. Astor attended religiously even in her dotage, but the real point seemed to be to rattle de Montebello, or simply to lull the jury into a stupor. And several jurors did appear to nod off.

But de Montebello quickly regained his balance when Mr. Hafetz asked him whether it was true that the Met stood to benefit from the ongoing litigation surrounding the Astor estate. Summoning the populism that rages in the recesses of every great museum director’s heart, inextinguishable no matter how many decades he spends in the company of Astors and Rockefellers and de la Rentas, he corrected Mr. Hafetz. It wasn’t just the Met who stood to benefit from the litigation, he said, his erect posture becoming even more erect. It was “the Met … and every visitor and his family.”

Ralph Gardner, Jr. is freelance writer whose work has appeared in New York magazine, the New York Observer, The New Yorker and other publications.