These days, the word “forensic” conjures up an image of a technician on a “C.S.I.” episode who delicately retrieves a single hair or a chip of paint from a crime scene, surmises the unlikeliest facts, and presents them to the authorities as incontrovertible evidence. If “forensic linguist” brings to mind a verbal specialist who plucks slivers of meaning from old letters and segments of audiotape before announcing that the perpetrator is, say, a middle-aged insurance salesman from Philadelphia, that’s not far from the truth.

James Fitzgerald, a retired F.B.I. forensic linguist, brought the field to prominence in 1996 with his work in the case of the Unabomber, who had sent a series of letter bombs to professors over several years. Fitzgerald had successfully urged the F.B.I. to publish the Unabomber’s “manifesto”—a rambling thirty-five-thousand-word declaration of the perpetrator’s philosophy. Many people called the Bureau to say they recognized the writing style. By analyzing syntax, word choice, and other linguistic patterns, Fitzgerald narrowed down the range of possible authors and finally linked the manifesto to the writings of Ted Kaczynski, a reclusive former mathematician. For instance, the bomber’s use of the terms “broad” and “negro,” for women and African Americans, enabled Fitzgerald roughly to calculate his age. Both Kaczynski and the Unabomber also showed a preference for dozens of unusual words and expressions, such as “chimerical,” “anomic,” and “cool-headed logicians,” as well as the less familiar version of the cliché “You can’t have your cake and eat it, too.” A judge ruled that the linguistic evidence was strong enough to prompt him to issue a search warrant for Kaczynski’s cabin in Montana; what was found there put him in prison for life.

The pioneer of forensic linguistics is widely considered to be Roger Shuy, a retired Georgetown University professor and the author of such fundamental textbooks as “Language Crimes: The Use and Abuse of Language Evidence in the Courtroom.” Shuy is now eighty-one years old and lives in Montana. When I asked him to describe the origins of forensic linguistics, he referred me to an Old Testament story. After a confusing battle with the Ephraimites, the Gileadites were able to identify the enemy by asking them each to pronounce the Hebrew word “shibboleth.” If they pronounced the first syllable in the Ephraimic dialect, “sib,” instead of in the Gilead dialect, “shib,” they were killed. According to the Bible, some forty-two thousand Ephraimites failed that first linguistic test.

Today, one can study forensic linguistics at several schools. For those earning a master’s degree, the field offers job prospects also outside the courtroom. Immigration and Customs Enforcement hires language detectives to assist agents in evaluating asylum seekers. In such cases, forensic linguists interview applicants to verify that their accents and their use of idiom and slang match those of the country they claim to have fled.

Celebrities? They are all a bit weird…

Hadley Freeman on 22 years interviewing stars.

I started working at the Guardian in the summer of 2000 – not to write, but to look after a key. The key to the fashion cupboard, to be precise, I had to (26) … no clothes for the fashion shoots were stolen.

Nonetheless, soon after I started, section editors asked which celebrities I’d like to interview. I was flabbergasted to say the least. In fact, as well as being an enthusiast, I am nosy, and this has occasionally got me into trouble in Britain. In New York City, where I’m from, it’s pretty much standard for two strangers on the subway to chat about what prescription meds they’re on, what crazy neighbours they’ve got, about the district or town they live in. In London, there are people I’ve known for more than 20 years and I wouldn’t dare to ask them if they dye their hair or recently had a job promotion. However, here, celebrity interviews, I quickly realised, are a context in which obnoxious nosiness and candor are not just accepted but expected. It still amazes me that so many celebrities will answer the bluntest of questions about their unhappy childhood/deepest trauma/ugly divorce in exchange for a mention of their movie in a newspaper, it’s an undertaking I am repeatedly thrilled to exploit. It has been the rare week in the past 22 years when I haven’t thought: I can’t believe I’m doing it as a job.

But initially I had some concerns about interviewing famous people for the Guardian. As I’ve said, I’m

an enthusiast, but I wasn’t sure if my tastes would really gel with Guardian readers. A bigger problem was that I had absolutely no idea what I was doing, as a glance at the transcript of my first interview for the paper proves. It was with Simon Amstell and Miquita Oliver, hosts of the Channel 4 show Popworld, which I adored, and fortunately for me, as well as being my first interview, it was theirs, too, so the three of us were equally clueless.

Others have been less understanding. When I made the rookie error of turning up to interview the shoe designer Christian Louboutin in a pair of very (27) … ballet pumps, he sniffily informed me that if I were a shoe, I’d be “a DM boot”. Robert Downey Jr was similarly unimpressed and took one look at my less-than-polished twentysomething face and expressed amazement that the Guardian had sent “the work experience girl” to interview him. As a hardwired people pleaser, these kinds of interactions initially unnerved me. But I soon learned that this gave me inner strength and helped me slough off my childish people-pleasing ways.

The most common question I get from readers is what the celebrities I’ve interviewed are like. That’s easy: they’re weird, because wanting to be famous is a weird thing and living your life as the object instead of a subject is a genuinely maddening way to exist. Generally, celebrities are very good at being celebrities, such as George Clooney and Tom Hanks, and many others, who maintain such a commitment to their brand images that they retain the facade even during interviews. It must be exhausting to be them – always on – but at least they make being famous look more fun than most.

It took me a while to let readers know how weird I am. It happened inadvertently, when the editor sent me to the US to interview Michael J Fox about his new sitcom. I adored him. I was so overwhelmed by my lifelong (28) … of Marty McFly and my now deep love for Mr. Fox himself that I let my full enthusiastic nature show in the article. I was a little trepidatious the night before the article out – would I be laughed out of the paper?

To my amazement, readers seemed to like the piece. From then on, I went full tilt with my enthusiasms: I interviewed pretty much all of my childhood idols – Mel Brooks, Rob Reiner, Ivan Reitman, Frank Oz – and I was delighted by how many Guardian readers shared my love for them. When I was overcome by Keanu Reeves’s (29) … and charm to the point I was barely able to ask him a question, Guardian readers gave me sympathy rather than the snark I expected.

There is now a mentality – popular in some progressive circles – that to give someone “a platform” (interview them) means you endorse them. But this is only true if you write puff piece interviews, whereas I like to have what Mrs. Merton used to call “a heated debate”, or what I call a conversation. I feel free to express my own and at times very different opinion. So I argued with Jeff Koons in New York about politics and art, and I argued with Margaret Atwood about gender. PRs, of course, hate this, because they think a journalist’s job is to transcribe unquestioningly whatever the celebrity said, but I know that’s not what readers want. It is definitely not what I want when I read an interview.

As well as writing interviews, I also wrote columns, and as a columnist, the temptation is to be definitive about an issue, focus on the ringing black and white and not the more complicated greys. But people are rarely black and white, which is why they’re so interesting. Charlie Sheen was a fascinatingly grey interviewee, someone who had done terrible things, but was smart and surprisingly self-aware and trying to figure out how to live with HIV. Woody Allen is now widely painted as A Bad Man, generally by people who have only the most skating knowledge of the accusations against him. I will always be grateful for the chance to interview him and later his son, Moses, and for giving me the space to (30) … the allegations. Journalism is about asking questions and refusing to accept whatever the currently accepted narrative is, whether it’s about politics or celebrities. It is not about getting likes on Twitter.