August 9 marks the 50th anniversary of the murder of Sharon Tate. The grisly homicide carried out by four members of the Manson Family (a commune and cult led by Charles Manson) has been widely discussed and dramatized in popular culture, and on July 26, Quentin Tarantino's Once Upon a Time...In Hollywood will tackle the topic once more. The film highlights a cast of characters from that era of Hollywood. Some, like Bruce Lee and Tate are real, while others like Rick Dalton (Leonardo DiCaprio) and his stunt double Cliff Booth (Brad Pitt) are pure fiction. But there is at least one 1960s California icon whose absence from the film we consider to be a glaring omission: Joan Didion.

In the titular essay of her 1979 book The White Album, Didion outlines the chaotic dissonance of the '60s. She writes of witnessing The Doors record bits of their third studio album, recalls the shooting of Huey Newton, and muses on the senseless killing of Tate in 1969. "Many people I know in Los Angeles believe that the Sixties ended abruptly on August 9, 1969, at the exact moment when word of the murders on Cielo Drive traveled like brushfire through the community, and in a sense this is true. The tension broke that day. The paranoia was fulfilled," Didion says.

Tate (who was pregnant with her husband, Roman Polanski's, child at the time) was murdered at the couple's home along with their houseguests Jay Sebring, Wojciech Frykowski, and Abigail Folger. Manson Family members Tex Watson, Susan Atkins, and Patricia Krenwinkel carried out the killings, under Manson's direction, while another Manson-ite, Linda Kasabian, served as lookout and getaway driver. Months later, some Manson Family members were arrested for automotive theft, and during that investigation police realized they had stumbled upon some answers in the Tate case. In December 1969, Kasabian turned herself in, and the following summer when the trials were underway, she became a key witness for the prosecution. In exchange for the evidence Kasabian offered to the authorities, she was offered immunity from prosecution, and became the only murder suspect to avoid prison.

During the 1970 trial, Kasabian became an object of fascination for the media, not least of all because of her fashion sense. Many reports remark that Kasabian's frocks were reminiscent of "peasant style" dresses or dirndls. What not many people know is that Didion was responsible for one such ensemble.

The choice of an outfit for the first day of court can be everything. In Kasabian's case, after she met with Didion while in protective custody at the Sybil Brand Institue before her 18 days of trial appearances, she evidently trusted the writer enough to make the decision for her. According to The White Album, Didion bought the dress Kasabian wore on July 28, 1970—her first day on the stand—from a now-shuttered San Francisco department store chain called I. Magnin. (I. Magnin went bankrupt in the '90s, and was acquired by Macy's.)

Didion describes the dress in detail:

In this light all narrative was sentimental. In this light all connections were equally meaningful, and equally senseless. Try these: on the morning of John Kennedy's death in 1963 I was buying, at Ransohoff's in San Francisco, a short silk dress in which to be married. A few years later this dress of mine was ruined when, at a dinner party in Bel-Air, Roman Polanski accidentally spilled a glass of red wine on it. Sharon Tate was also a guest at this party, although she and Roman Polanski were not yet married. On July 27, 1970, I went to the Magnin-Hi Shop of I. Magnin in Beverly Hills and picked out, at Linda Kasabian's request, the dress in which she began her testimony about the murders at Sharon Tate Polanski's house on Cielo Drive. "Size 9 Petite," her instructions read. "Mini but not extremely mini. In velvet if possible. Emerald green or gold. Or: A Mexican peasant-style dress, smocked or embroidered." She needed a dress that morning because the district attorney, Vincent Bugliosi, had expressed doubts about the dress she had planned to wear, a long white homespun shift. "Long is for evening," he had advised Linda. Long was for evening and white was for brides. At her own wedding in 1965 Linda Kasabian had worn a white brocade suit. Time passed, times change. Everything was to teach us something. At 11:20 on that July morning in 1970 I delivered the dress in which she would testify to Gary Fleischman, who was waiting in front of his office on Rodeo Drive in Beverly Hills. He was wearing his porkpie hat and he was standing with Linda's second husband, Bob Kasabian, and their friend Charlie Melton, both of whom were wearing long white robes. Long was for Bob and Charlie, the dress in the I. Magnin box was for Linda. The three of them took the I. Magnin box and got into Gary's Cadillac convertible with the top down and drove off in the sunlight toward the freeway downtown, waving back at me. I believe this to be an authentically senseless chain of correspondences, but in the jingle-jangle morning of that summer it made as much sense as anything.

Of course there are photos of Kasabian from this time period, but it's hard to identify the exact dress purchased by Didion. It is described in The New York Times as "a blue and red, peasant-type gown." One of the widely circulated photographs of Kasabian from that era is this one, in which she appeared in 1971 wearing a similar dress. There is also this orange frock, which she wore near the end of the trial at a press conference in Los Angeles. Many photos of Kasabian during the trial project an image of girlish innocence, which she pulls off partially because of her sartorial decisions. The "long white robes" worn by Bob Kasabian and Charlie Melton can be seen in photographs from the trial, but a photograph of that I. Magnin dress purchased by Didion seemingly evades the Internet.

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We speak often of the trend of cult-like fashion permeating the general consciousness. The flowy, all-white robe ensemble is one way to look like a member of a cult. The matching red separates popularized by the Rajneeshee is another. Wearing a long, white robe on the first day of court would not have helped Kasabian's case; she might have come off as loyal to Manson, when her intention as the key witness for the prosecution was quite the opposite.

In Once Upon a Time...In Hollywood, the Manson Family cult members are depicted as a mix of real and fictional people. For example, Dakota Fanning plays Squeaky Fromme, the real-life Manson Family member who also attempted to assassinate President Gerald Ford in 1975. A character possibly modeled off Kasabian is played by Maya Hawke, who stays behind in the car while the murders take place. (A previous pop culture iteration of the Tate murders—American Horror Story: Cult—shows Kasabian as portrayed by Billie Lourd.) The events of Once Upon a Time...In Hollywood take place in 1969, before the trial began. Still, costume designer, Arianne Phillips, even Instagrammed a fabric rendition of the book cover for The White Album, which suggests she must have done her homework.

As is typical of many films helmed by Tarantino, save for Jackie Brown and the Kill Bill franchise, the female characters are somewhat underdeveloped in Once Upon a Time...In Hollywood. Margot Robbie receives top billing alongside DiCaprio and Pitt for playing Tate, an important focal point of the narrative, but she has a minimal number of spoken lines whenever she appears on screen. The Manson Family women, too, get less screen time that one would hope. Who wouldn't rather watch a version of this story that follows the women who committed unspeakable crimes, and features a scene in which Didion (played by Carrie Coon, perhaps) goes shopping for the dress she gives to Kasabian?

Court room style has become a popular subject of intrigue. Anna Delvey, otherwise known as the SoHo grifter, appeared at her New York trial wearing a skinny black choker, thick-rimmed glasses, and ballet flats, after she was urged by her lawyer to avoid wearing stilettos. Page Six had a field day when Cardi B appeared at the Queens Supreme Court wearing Louboutins and Ferragamo last month. (The rapper was not thrilled with the reporting, insisting that she dresses "like a f--king lady" in her designer threads whenever called to court.). Even on the fictional Big Little Lies, Celeste (Nicole Kidman) armors herself in an ultimate courtroom showdown against her mother-in-law, Mary Louise Wright (Meryl Streep), with a demure blazer over a bland blouse, so as to project both her innocence and her ability to be a good mother. The point is, what is worn to a trial—real or fictional—has always mattered. Imagine having Didion—a style icon herself—pick our your first-day-of-court outfit. Now that is a stranger-than-fiction tidbit of history that seems made for Hollywood.

Related: Once Upon a Time in Hollywood: Everything We Know About Quentin Tarantino’s Manson Family “Masterpiece”