LONDON — Prior to making “Off The Rails,” Adam Irving’s previous foray into the world of documentary film-making had been a student short about competitive Ivy League university ballroom dancing. His first feature, however, posed much greater problems, not least because its subject, for most of the three years Irving spent making the film, was incarcerated. Telling the story of Darius McCollom, the film begins in a somewhat light-hearted manner, revealing its subject as a Robin Hood figure whose crimes, bizarrely, involve “hijacking” New York buses and subway trains – and simply driving them to schedule. The authorities, however, have yet to see the funny side, and although McCollum has been diagnosed with Asperger’s, the 51-year-old has spent almost half of his life in jail.

Directed, produced, shot and edited by self-confessed “control freak” Irving, “Off The Rails” not only raises awareness of McCollom’s plight, it also paves the way for the inevitable studio version. Titled “Train Man” and directed by John Crowley (“Brooklyn”), it will tell the story from the point of view of McCollum’s longtime lawyer Sally Butler, to be played by Julia Roberts.

“I anticipate that it will have an effect,” says Irving. “At festival screenings I get asked a lot, ‘Adam, what are you doing to help Darius? Is there a website? Is there a foundation we can give to?’ It’s sort of beyond my powers and resources as a filmmaker, so I haven’t taken it upon myself to create some sort of movement. But I am very confident that when the Julia Roberts movie comes out next year – which will be a hundred times bigger in its scope and advertising budget than my film – that is going to have an impact.” Variety talked to Irving at London’s Raindance Festival

How did you get into filmmaking? 

I had a moment when I was a teenager when I discovered the joy of cinema and decided I wanted to be a film scholar, a professor like my father, so I did a Master’s degree and a PhD. The idea was to teach film history – film theory, film criticism, that kind of thing – but I dropped out of my PhD programme, moved to LA and decided to make documentaries instead.

Why was that?

Because within cinema it’s the most academic [discipline], and it reminded me the most of the process of writing a book or a thesis. Because you do your research, you have your argument – or several arguments – but instead of using words you’re using images to make your point.

How did you first get involved with Darius McCollom?

I actually lived in New York for a couple of years and I’d never heard of him. It wasn’t until I moved to Los Angeles and decided to become a documentary filmmaker that I began looking for ideas. I came upon his Wikipedia page after reading a different page about people who were obsessed with trains, and it gave him as an example. So when I clicked on his article, I was hooked – the first line of his Wikipedia page reads like a logline for a movie.

How easy was it for you to get in touch with him?

He was incarcerated at the time, so it was not easy. I had never in my life known convicted criminals, so I had no idea how to write to, or visit or call someone who’s incarcerated. But what I did do is, I flew out to New York and met Jude Domski – she’s in the film – who wrote a play about Darius called “Boy Steals Train,” and she had a professional relationship with him. She told me how to get in touch with him, and so I exchanged over 100 letters and phone calls with Darius over the course of six months, building his trust and getting to know him before I visited him in jail, in person, about six months later.

How was he?

He was very co-operative. He loves attention, he loves his story being told. He wants fame and fortune – he’s not embarrassed to say that.

Did anything surprise you about Darius’s story?

Not a ton, because I did a lot of research and I read a lot about him, so there weren’t any parts of his life that were big surprises. It was more [about] dealing with him as a human being. He was just shockingly normal. He does not come off as someone who has spent 20 years in maximum security prison, with all the abuse and loneliness and fear… He just is always even-keeled and jolly, and it’s something I never got used to.

Why isn’t he worn down by it?

Adam Irving: I think part of it is the Asperger’s, because it may well have worn him down, but either he’s not aware of it or he can’t express it, because he’s more logical and numerical than emotional. So it either gets buried or it’s there and he just doesn’t know how to express it. The other thing is, as Darius says, you can get used to anything. After 20 years of anything, if you’re fighting in wars in the military, eventually you get used to it – or go crazy.

Where is he now?

Adam Irving: He is in New York, in jail, in Manhattan Detention Complex awaiting trial for a crime that he committed.

Did you always see the film as a tool to raise awareness of his situation?

Adam Irving: I saw it quite late in the process, to be honest. When I started the film, I envisioned it as a lighter, quirkier film, sort of like “Catch Me If You Can”, the Tom Hanks-Leonardo DiCaprio movie, and I thought it would be a tale of his life and all his escapades – there would be suspense and humour, and somehow it would all just work out at the end of this quirky story. But as I got pretty far in the editing process and started testing it out on friends and family, I found that what people gravitated towards was the injustice of it, and the sadness, so I started making the film bigger than just about Darius, widening it out so that it’s a critique of the American criminal justice system. That’s when I brought in a professional editor to help me craft the film to be more serious, more deep and more of a social justice piece that could not only change Darius’s life but other people like Darius.

What’s next for you?

I am so afraid of my next film not being as good as this one. I’m desperately looking for ideas, but because promoting the film was kind of a full-time job, I haven’t really given it serious thought. But beginning in January, once my film is fully out there, I’m going to start looking. I hope to do another character-driven film – because those are the ones that really excite me – rather than [make] a broad issue-oriented documentary about global warming or the war in Syria.