On a warm summer's evening in June 2001, a Navajo Indian teenager from Cortez, Colorado, left his mother's trailer home to visit a nearby rodeo that had pitched up on the outskirts of their reservation. Growing up in such a remote corner of conservative Middle America, Fred Martinez was always going to stand out from the crowd.
From a young age, he had chosen to dress in an openly feminine way, meticulously plucking his eyebrows into sharp lines and coating his eyelashes in mascara. On the last night of his life, as he waved goodbye from the dusty path leading away from the trailer park, his mother noticed that her 16-year-old son had chosen to wear a bra, stuffing the cups with a pair of socks.
It was five days before police found Fred's body and another two weeks until they arrested his killer. Shaun Murphy, an 18-year-old with a string of previous convictions, had spent the fortnight openly boasting to his friends about how he had recently "bug-smashed a fag". Fred Martinez became one of the youngest recorded victims of hate crime in modern American history. As the press followed Murphy's trial, the inevitable questions were raised over how someone could kill another human being purely because of their sexuality.
But for Lydia Nibley, a 47-year-old, LA-based film-maker, there was an even more important story shining through the tragedy of the teenager's murder.
"I didn't want to shoot a true crime documentary," she explained earlier this week as she prepared to travel to London for the BFI's annual Lesbian and Gay Film Festival. "For me, Fred's short and beautiful life shone a light on the incredibly rich subject matter of the Native American understanding of gender."
Most people in the Western world would probably describe Fred as either a gay or transgendered teenager. But the Navajos had a different word for people like Fred. They would call him nadleehi, literally, "one who constantly transforms". Like many Native American cultures, the Navajo believe gender is more complicated than just male, female or transgender. Masculine and feminine is a fluid concept that can change over time. In their eyes some men possess feminine traits, while some women have manly attributes. Others take on separate attributes at different stages of their lives. The Navajo have four recognised genders, other tribes have as many as seven.
Christian missionaries and centuries of white colonialism have done much to wipe out such customs. Although Fred's mother recognised and supported her son's nadleehi status, family members who had converted to Christianity were far less sympathetic.
But it was through Fred's death that Nibley stumbled into this world to discover the Navajo's once elastic and tolerant approach towards gender.
The result is Two Spirits, a powerful documentary shot over five years that is creating waves among native American activists who have long wanted ordinary tribe members to reconnect with their ancestral approach towards sexuality. The film will have its UK premier this weekend at the London Lesbian and Gay Film Festival (LLGFF), the country's largest showcase of gay cinema, of which The Independent is a media partner.
"The Navajo once placed enormous importance on nadleehi," explains Nibley. "Had Fred lived in another time he would have been considered an immensely important and sacred person. Instead, he died tragically early at the hands of a bigot."
For Brian Robinson, the senior programmer of the LLGFF, Two Spirits is one of a host of documentaries that, he believes, show how far gay cinema has come in the past two decades.
"There's an enormous appetite at the moment among gay film-makers to seek out those interesting stories that tell us something we might not know," he says. "It's a mark of how mature gay cinema has become. We're a long way now from the Seventies when it was all positive role-model stories and identity politics."
As another example he cites Stonewall Uprising, which receives its world premier at this year's festival, now in its 24th consecutive year. Directed by Kate Davis and David Heilbroner, the feature-length documentary explores what many regard as the spark that lit the modern gay rights movement.
Told by those who took part in riots following the 1969 police raid on the Stonewall Inn in New York's Greenwich Village, the film features a rich trove of archival footage and modern-day interviews, which piece together the moment America's gay community began to fight for their rights.
"Stonewall is one of those events that the gay community think they know but actually our knowledge is often quite limited," explains Robinson. "Through this film you get to see the bar where the raid took place, hear the words of the police officer that led that raid and understand who the people were who began protesting."
But documentaries are not the only films causing a buzz at this year's festival. Over the next few weeks the BFI, and a small number of cinemas across central London, will show more than 240 films by lesbian, gay and transgender directors from as many as 29 different countries. The festival will then tour Britain over the next three months, spreading some of the world's finest gay cinema far and wide. It is a legacy that the Stonewall rioters can be proud of.
Take, for instance, the festival's opening offering this year, The Secret Diaries of Miss Anne Lister, which was shown on Wednesday evening for the festival's launch at the Odeon West End in Leicester Square. At first glance, the film looks like any other BBC costume drama, but this is no Sense and Sensibility.
Anne Lister (1791-1840) is often described by gay activists and historians alike as Britain's first modern lesbian. A Yorkshire landowner, industrialist, traveller and diarist, she was also a lesbian who meticulously recorded her love affairs in more than four million words. Much of her sexual experiences were written in code and were only cracked in the late-20th century.
Now, with the Shameless star Maxine Peake playing the lead role, it has been given a BBC makeover and prime-time billing, due to air on BBC2 later in the spring. "Lister was an extraordinary woman who, up to recently, has only really been documented in lesbian history," says Peake. "Hopefully, with this film and documentary, she will reach a wider audience exposing them to this inspirational and formidable woman."
Contemporary dramas also feature prominently this year. Michael Blyth, another festival programmer, particularly recommends the French-Canadian film I Killed My Mother, the writer, director and star of which is the 20-year-old Xavier Dolan.
"It's the story of a teenage boy and the turbulent relationship he has with his mother," explains Blyth. "But for me, what makes the film so exciting is that the character he plays is a 16-year-old boy who doesn't go through any issues about his sexuality. That's not the focus of the film.
"He doesn't go through a coming-out process and I think that's something that's really interesting, because quite often gay teen films are coming-out stories. The fact that the film takes his sexuality as a given makes it a very contemporary and fresh kind of work."
BFI London Lesbian and Gay Film Festival, BFI Southbank, London SE1 (020 7928 3232; Bfi.org.uk/llgff/) to 31 March. Media partner: The Independent
GLOBAL RANGE: FESTIVAL HIGHLIGHTS
The most detailed account yet of what happened during the 1969 Stonewall riots, a spontaneous night of protest and riots that effectively launched the modern-day gay rights movement. Receives its world premier at this year's festival.
I Killed My Mother (J'ai Tue Ma Mere)
The 20-year-old French- Canadian director Xavier Dolan has wowed film critics over the Atlantic with his searing, semi-autobiographical film about a gay teenager's turbulent relationship with his mother. Dolan wrote the script, directed the film and stars in the lead role.
The Secret Diaries of Miss Anne Lister
A BBC-commissioned period drama about Britain's first modern lesbian. The 'Shameless' star Maxine Peake stars as Anne Lister, a landed Yorkshire aristocrat from the 19th-century who chronicled her lesbian affairs. Opens this year's festival and will also be broadcast on BBC2 later in the spring.
Screened to praise at Berlin last month, this documentary chronicles the short and extraordinary life of Candy Darling, a favourite of Andy Warhol and one of the first American transsexual celebrities to gain mainstream celebrity and acceptance.
Children of God
A love story between two young males, set in the Bahamas against a backdrop of rising anti-gay protests. Shot by the Bahamian director Kareem J Mortimer, 'Children of God', which closes this year's festival, is unusual for its portrayal of homophobia in the Caribbean.