One day I can be interpreting at a Premier League football club, the next I can be sitting in a high-security prison

I’m a talker: I’ll have a conversation with anybody. But as a professional French-English interpreter working in the criminal justice system, I can be a different person’s voice every day. I’ve translated for murderers and suspected terrorists.

I remember my first job in a crown court. I was 27, in the dock with a drug smuggler who had been paid to carry cocaine in her suitcase from South America. She was about my age, with a child. I could feel my heart pounding before I opened my mouth. She was found guilty and sent to prison. Every case I’m involved in hangs on the accuracy of what I say; when someone’s life or freedom is on the line, I feel additional pressure.

I translate verbatim and in the first person. To add or omit anything would distort the dialogue. I have to find the right words and register, but I’m also required to mirror emotion and intonation. Silences are important, too; they are all part of how we converse. The way words are delivered changes a whole message. You feel a bit like an actor at times. I once spoke for a doctor accused of manslaughter who was so desperate to prove his innocence. For that day, I felt that I became him.

Cultural nuances can be crucial. We understand “mon frère” to mean “my brother”. In African cultures it can be “my friend”, too. Whether a brother or friend arranged to get someone out of prison can change a whole asylum case.

It’s not just about being bilingual; I work with different lexicons. Communicating court terminologies is different to speaking for an asylum seeker in counselling, or a child in speech therapy, where a professional relies on my exact delivery to form a proper opinion.

I did a French degree followed by a masters in translation and a diploma in public service interpreting, which trains you to speak in police, local government, health or legal settings. One day, I can be interpreting at a Premier League football club, translating for a footballer receiving a drugs ban; the next, I might be sitting in a high-security prison.

The criminal stuff is really my bag; a world that’s not my own. I love being a fly on the wall. I spent two days in a police control room listening into a wiretap in a high-profile unsolved murder case. In reality, there was a lot of him turning on his TV and flushing the toilet, but it felt like a civic duty.

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The conversations I am part of are confidential and often traumatic. I have repeated explicit sexual assault details, spoken for a teenage girl who had been trafficked into prostitution, and translated for a torture victim – but I can’t discuss any of it with a friend on the way home. I have to deal with them in my head, which can be hard.

Everyone has their limits. I find the health stuff hardest, particularly where children are involved as, at 36, I’m a mother myself. I had to tell one lady that she had cancer. It was the only time I’ve cried in a job.

But these conversations are a privilege, too. I have acted as a birthing partner for women who are otherwise alone. One lady, an asylum seeker, asked me for baby names during labour. I had watched Peter Pan that weekend; she called her daughter Wendy.

Often I’m part of life-changing dialogues that are left on a cliffhanger. I interpreted for a foreign student arrested after a crash in which someone died. He was petrified. I don’t know if he was prosecuted, but I’ve thought of him often since.

My job has opened my eyes. When you’ve spoken, first person, for an asylum seeker who was left to rot without food or daylight because they were gay or didn’t support their government, it makes me furious to hear people say they shouldn’t be here.

I recently spoke for a scared teenage girl in a Home Office interview. It took everything not to put my hand on hers. Her solicitor pointed out each member of the team there to support her. “Lauren is your mouthpiece,” she said.

I’m not the doctor, the police officer or the judge in these rooms; I’m just somebody who did a French degree and loves languages. I feel honoured to be part of those dialogues. These conversations couldn’t take place without me.

• As told to Deborah Linton

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