Donovan Tavera: 'Corruption and impunity keep the violence in Mexico going' © Bénédicte Desrus

One day, when I was 12, I looked down from the window of our apartment to see a body lying dead beside a street-corner taco stand, his blood pouring into the gutter. He was the victim of a car accident. When I asked my mother where the blood would go, she couldn’t answer. The next day, I saw the taco-stand owners throwing soap and water over the blood. By midday, it was business as usual. That seemed so sad. I decided that if no one else was going to care about these things, I would.

The career of forensic cleaner barely exists in Mexico. I taught myself everything. My teenage years were spent in the library and the garage, replicating dried blood and other substances, and inventing the formulas to clean them. I’ve invented more than 300 of them.

The police here in Mexico leave a mess at murder scenes: fingerprint dust, footprints, scraps of evidence. Families find me over the internet or through word of mouth. I’m liked because I’m discreet. I come in, I do my job and I’m gone. Relatives look so tired and sad when they show me where to clean but so much lighter after I’ve finished. I help with their grieving process.

In the 15 years since I went professional, I’ve done hundreds of cleanings nationwide, from multiple homicides in Mexico City to suicides in Tijuana. My formulas are the difference between me and other cleaners who simply use bleach and water. Most people think that “clean” just means that the smell and stains are gone. But blood is dangerous. TB, HIV and hepatitis all remain live at a scene, if they are present in the victim. Stabbings leave blood mixed with pericardial fluid, which spreads separate contaminants. To clean a shooting, you need many formulas for many different bacteria, because a bullet cuts through several tissues.

It’s frustrating to have to convince people that my job is necessary. At police stations, when I explain my work, even the detectives look at me as if I’m strange. If they call me to clean, I have to pay them a cut of my fee. This hurts. My most expensive jobs — a multiple murder, or a long-term decomposition — cost $400. In America, I could charge $2,000.

I have a young daughter, and my parents, uncle and wife all work with me. Last year, we got hardly any cleanings and suffered terribly — straight zeros in the bank account. But we believe in this job. Corruption and impunity keep the violence in Mexico going. Taking care of the dead is part of the solution.

When I’m cleaning, my emotions freeze. I enter a trance. I don’t notice the time: there is too much to focus on. I begin by scraping off the dried stains, before adding formulas to kill bacteria. I disinfect and bag the trash, then do a basic clean-up. By the time I leave, the place looks like nothing has happened there.

One case was traumatic: eight people were murdered in one apartment. Even without the bodies, I saw the whole murder again like a film in my head: people running, their faces, knives coming down, the splatter marks from where they had tried and failed to defend themselves.

At home, I relax by listening to Wagner or Bach: by contrast, when cleaning, I’ll put on Black Sabbath. I read psychology and detective novels. Sherlock Holmes is one favourite. It’s contrived, of course, but I love that he has an answer for everything.

I don’t like to go out during the day: there’s too much noise, chaos, traffic. At night, though, I drive around the city listening to Mexican songs from the 1950s. I stick to AM radio stations because there’s no news. That way, I can pretend I am in a more innocent time, a more innocent country. I park beside the Angel of Independence monument, smoke cigarettes, watch the cars, and wait for my next job.

Photograph: Bénédicte Desrus

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