The riveting documentary The Case Against 8 takes an in-depth look at the historic federal lawsuit filed in an effort to overturn Prop 8, California’s discriminatory ban on same-sex marriage. Shooting over five years, with exclusive behind-the-scenes footage of the powerhouse legal team of David Boies and Ted Olson and the four plaintiffs in the suit, directors and producers Ben Cotner and Ryan White (Good Ol’ Freda, Pelada) have created a powerful emotional account of the journey that took the fight for marriage equality all the way to the U.S. Supreme Court.

A crowd-pleaser on the festival circuit, The Case Against 8 won the 2014 Sundance Film Festival Directing Award in the U.S. Documentary category and the SXSW Audience Award in the Festival Favorites category.

In May 2008, the California Supreme Court legalized marriage for same-sex couples in the state. Some 18,000 couples were married in the next few months, but the backlash was swift. Six months later, a coalition of conservative forces placed a proposition on the November statewide ballot that defined marriage as exclusively between a man and a woman. After a fiercely contested campaign that drew national attention, the controversial initiative known as Prop 8 passed with 52 percent of the vote, resulting in an amendment to the state constitution banning marriage for same-sex couples.

Stunned by the passage of Prop 8, activist Chad Griffin and his colleagues decided they needed to act immediately and formed the American Foundation for Equal Rights. A chance meeting pointed Griffin to an unexpected ally: Ted Olson, lead counsel for the Republicans in the critical 2000 Bush v. Gore Supreme Court decision and solicitor general under President George W. Bush, was interested in taking on the case. In contrast to many of his conservative colleagues, Olson believed in the right to marry for all loving couples.

“Marriage is a conservative value,” Olson explains in the film. “It’s two people who love one another and want to live together in a stable relationship, to become part of a family and part of a neighborhood and part of our economy. We should want people to come together in marriage.”

Not only did Olson agree to lead the legal team that would challenge Prop 8, he made a surprising recommendation for his co-counsel: David Boies, the attorney who opposed him in Bush v. Gore. Although they held dramatically different beliefs on many political issues, both had become an admirer of the other during that trial. Now, they had found a case they could pursue passionately together, all the way to the Supreme Court of the United States.

The unlikely pairing of Olson and Boies sparked outcry from both sides of the aisle, as conservatives protested that Olson was turning his back on traditional principles, and liberals and the LGBT community accused Boies of collaborating with the enemy. But, as Boies puts it, “Everybody on that case had a sense that what was important was the mission.”

Just as important as the legal team that would argue against Prop 8 were the two couples who would become the faces of marriage equality in California. After a lengthy vetting process, Kris Perry and Sandy Stier, and Jeff Zarrillo and Paul Katami, were selected as the plaintiffs in the case that would be known as Perry v. Schwarzenegger.

Kris and Sandy, the mothers of four sons, first attempted to marry in California in 2004, during the brief period when marriage licenses were issued to same-sex couples by the city of San Francisco. When their original marriage was declared void, their family was devastated and confused. Comments Sandy, “We receive a form letter in the mail saying, ‘You thought you were married, but you’re not.’ What does that say to these people that we invited to celebrate our love for each other? I felt badly for making them feel badly for us. It’s just this awkward circle of guilt and shame.”

Jeff and Paul were ready to start a family, but hesitated to have children without the traditional status and legal protections of marriage. Jeff explains, “We’re strong believers that we want any child that we have to have the protections that an opposite-sex couple’s children and family would have. That’s very important to us.”

In intimate interviews, both couples speak frankly and emotionally about the effect of the law on their lives and families, and about how their participation made them highly visible targets of hatred. Their decisions to join the lawsuit brought unwanted attention and anonymous threatening phone calls, but all four stayed the course, meeting with the attorneys to prepare for court appearances over the five years of the case.

“I’ve never been as nervous in my life,” says Paul before their first court appearance. “Even though we’re ready, there is the weight of ‘I can’t mess this up.’ I have to represent so many people.”

The Case Against 8 follows lawyers and plaintiffs from confidential war-room strategy sessions to last-minute trial preparation. From the Federal District Court in San Francisco to the 9th Circuit Court of Appeals and finally to the Supreme Court, Olson, Boies and their associates masterfully build a case with testimony from an army of experts, finally effecting a stunning last-minute reversal that Olson calls the “Perry Mason moment”: an admission from an opposition witness that changes the course of the trial.

Paul and Jeff were among the first same-sex couples to be married in California in 2013. Paul explains, “The right to get married is, to me, a civil right…so by accepting a domestic partnership, we’d also accept being second-class citizens. And that was unacceptable to us.”

Ted Olson proudly calls the Prop 8 suit “the most important case I have ever worked on.” Today, the fight continues: As of May 23, 2014, 19 states and the District of Columbia have legalized marriage for same-sex couples, while 31 states explicitly ban it. Lawsuits challenging the bans are in progress across the country and marriage equality has become one of the most visible and important civil rights issues debated today.

Director and producer Ben Cotner has served as an executive for ten years at Paramount Pictures and Open Road Films, where he most recently oversaw acquisitions and production. He has worked on such films as An Inconvenient Truth, American Teen, Mad Hot Ballroom, A Haunted House, Side Effects, The Grey” and End of Watch.

Director and producer Ryan White is also the director and producer of “Good Ol’ Freda,” which tells the story of Freda Kelly, the Beatles’ longtime secretary, and Pelada, a journey around the world through the lens of pickup soccer. White’s other credits include Capitol Crimes and 9/11: For the Record on PBS; Dead Wrong: Inside an Intelligence Meltdown on CNN; and Country Boys on PBS’ Frontline.

The Case Against 8 is directed and produced by Ben Cotner and Ryan White; editor, Kate Amend, A.C.E.; music by Blake Neely; associate editor, Helen Kearns; co-producers, Rebekah Fergusson and Jessica Lawson; associate producer, Carin Bortz. For HBO: supervising producer, Sara Bernstein; executive producer, Sheila Nevins.