A WEEK AFTER her husband, car inventor John De Lorean, was arrested, Cristina Ferrare flew to Manhattan, bought a somber wardrobe from designer Albert Capraro and had trendy stylist Suga snip off her shoulder-length hair because, a spokesman for the New York hairdresser said, "she needed a change."

That change coincided with the court appearance last week by her husband, charged with setting up a $24 million cocaine deal. When the cameras focused on Ferrare, looking more like Joan of Arc in designer sackcloth than a Vogue fashion model with a well-publicized penchant for sables and jewels, lawyers all over the country recognized the syndrome. Cristina Ferrare was dressing for acquittal.

"I tell my clients to dress conservatively," says Joseph Ball, De Lorean's Los Angeles attorney. "I don't want them in fancy pants or cowboy boots." Ball denies that he told Ferrare to cut her hair or buy a new wardrobe, but he is obviously pleased with her new look. Ball has a definite image in mind for all his clients. "I want them to dress like they're going to a wedding," he says.

Veteran Washington trial attorney Sol Rosen thinks Cristina Ferrare's new haircut will help De Lorean's case. "The jury will see a picture of very short hair, very conservative," he says.

Most lawyers agree: The defendant is not the only one on trial.

"Particularly in the De Lorean case," says Washington attorney Peter Kinsey, whose law firm handled Rita Jenrette's divorce from her husband John, the former Democratic congressman from South Carolina who was convicted in the Abscam bribery scandal. "His whole life is on trial. His wife is somebody they're going to be looking at. The jury's going to be looking at her, her dress, demeanor etc."

Washington attorney Kenneth Robinson thinks he might have been able to win the Jenrette case if Rita Jenrette had, in his words, toned down her "sexpot" image.

"I always felt when I defended John Jenrette that Rita Jenrette dressed totally inappropriately," Robinson says. "We had fights over it."

When Rita Jenrette accompanied her husband to his preliminary hearing in U.S. District Court here wearing a tight, low-cut blouse, Robinson was angry. "I told her to stop doing that. She said, 'This is the way John likes me. I dress for John.' I said, 'You have to dress for the jury now and the jury doesn't want to see that.' "

So Rita Jenrette, according to Robinson, went to Neiman-Marcus and bought a new wardrobe, which included designer outfits by Calvin Klein. But her concessions to the prim, lady-like look the lawyer wanted were few. While in one outfit, her demure white blouse was tied at the neck with a schoolgirl bow, her tight skirt was slit up the thigh. "I got furious," Robinson recalls. "We're portraying John as totally broke and you show up with a $1,000 wardrobe. John wore the same suit every day, the one with a cigarette burn in it, looking totally down and out. She should have worn cotton blouses, not silk."

Did Rita Jenrette's wardrobe cost her husband an acquittal?

"She came in looking like a sexpot and that was not good for John. Who's to say it swayed the jury?" Robinson asks. "They looked at her and saw a glamorpuss. Which meant he either had money or the motive to get money."

Rita Jenrette strongly disagrees.

"Since he didn't win the case, it's easy to blame the wife," she said from her Los Angeles home. "I did as much as I could without wearing a full-length black Victorian dress and hiding my face behind a veil. I don't think you can attribute a conviction or non-conviction to the way the spouse dresses. Either you have a case or you don't."

Rita Jenrette says she thought enough to buy blazers and suits at Neiman-Marcus (clothes which she's since given to her mother) and wore the slit skirt only one day. She got so many letters of objection that she never wore it again. She also says her mink coat--another matter of contention between her and Robinson--was necessary. "I wasn't going to freeze to death. Robinson said, 'The judge's wife wears a cloth coat. You have to wear a cloth coat.' Well, I didn't have a cloth coat."

Jenrette says she resents Robinson's suggestions, but isn't surprised by them. "It was just an extension of what I had gone through with John's staff for the previous five years," she says. "You can't change the way your body is. When I saw Cristina Ferrare on the news I had such empathy for her. I know what she's going through. I'm sure somebody told her the same thing they told me, 'Get your conservative wardrobe together.' "

Maybe the lawyers need more advice on what to wear, Rita Jenrette says. Kenneth Robinson's "pants were so big. He wore this big old suit. Trying to project this good ol' country boy image. That didn't get John off, either."

It's very simple, she says. "Nothing works except the truth."

Some lawyers are loath to get involved in the wardrobe question. Washington attorney Michael Tigar bristles at the notion that he might have made any dress-code suggestions to Katherine Murphy, wife of his former client John Murphy, during the former congressman's Abscam bribery trial. "I think the notion of a male lawyer telling the wife of a defendant to do this or that is the most incredibly sexist suggestion I've ever heard," Tigar says. "I think it's an insult."

Marvin Mitchelson, the celebrated Los Angeles lawyer who is most famous for winning the first "palimony" suit and who recently handled jet-setter Soraya Khashoggi's $2.5 billion divorce suit, does give wardrobe advice to his clients but says he never would have told Cristina Ferrare to cut her hair. "I don't think the jury is going to be influenced at all by the fact that she stepped out of the Middle Ages, ready to do penance by chopping off her hair . . . I would have advised her to let her hair alone."

Yet Mitchelson says he told his client Michelle Triola -- who was seeking "palimony" from her former lover, actor Lee Marvin -- to dress "like she needed the money."

Triola "changed a little bit," Mitchelson says. "I wanted her to look very down-to-earth, rather plain and simple." For his other celebrity clients, Mitchelson approaches the question of wardrobe with kid gloves. "I had Soraya pull back her hair," he says. "I didn't have to tell Bianca Jagger how to dress. But I made suggestions to Sarah Dylan, who was the barefoot type. I wanted her to dress up a bit. You have to do it very delicately."

He says he trys to keep women out of pantsuits, and prefers shoes with closed toes. "And I love horn-rimmed glasses," he says. "It suggests a bit of intelligence."

One woman whose appearance definitely made a favorable impression during the Watergate hearings was Maureen Dean, who radiated a cool sense of stylish innocence with her blond bun and huge doe eyes.

"I think Maureen Dean had a great impact on her husband's testimony," says Rosen. "She sat there at the hearings very prim, wore a new outfit every day."

Maureen Dean declined to be interviewed this week as did her husband. "I don't know anything about women's fashions," he said from their Los Angeles home.

In her 1975 autobiography, entitled, "Mo: A Woman's View of Watergate," the wife of John Dean went into great detail discussing her color-coordinated wardrobe for the nationally televised hearings. After her husband told her to dress "like a wife," Maureen Dean writes: "Not knowing his precise notion of what 'a wife' looks like, I relied on my own fashion instincts, choosing a very high collared tan dress to wear the first day. On Tuesday I picked out a combination that I loved -- a brown linen dress and a white silk blouse with brown polka dots. Wednesday I wore a floral blouse with a melon red suit, Thursday a white blouse with a bright yellow linen suit . . . On Friday I wore a burgundy blouse with white polka dots, a white skirt, and a navy blue blazer."

When she planned to wear a turban one day, her husband put his Gucci down. "That won't go well with Middle America," John Dean is quoted as saying.

One night, while her husband agonized over his next day's testimony, Maureen Dean could rest easy. "My own major decision -- what to wear," she writes, "had been made the night before."

And it's not only the wife, but the family and supporters as well who present an image that can influence a jury. "If it plays a role, it's a subconscious one," says New York attorney Joel Aurnou, who defended Jean Harris, convicted of murdering "Scarsdale Diet" Dr. Herman Tarnower. Harris' brother appeared in court one day wearing his naval uniform. But Aurnou says it wasn't a deliberate attempt to present his client in a conservative light. Her brother really was a naval captain.

In any case, lawyers suggest that changes, if any, be subtle. "I think it can hurt if you really change who you are and the jury recognizes it," says attorney Kenneth Robinson. "They see the whole thing as a con."

In the De Lorean case, he added, the jury is unlikely to be swayed by Cristina Ferrare's hair or clothes. "In a close call, it could be important."

Marvin Mitchelson says it's all psychological.

"In a case like De Lorean's, you want to look like, 'How did we get here? 'We don't belong here.' "