"I feel blessed by God that he gave me this face," he says genially. "When I walk into a production office, people immediately hire me as Inmate No 1."
Even interviewers are wary of Trejo on first acquaintance. Peacock tattoos adorn each arm, and the large image of a woman wearing a sombrero is just visible on his chest. The eyes are deep-set, and the face so battered he makes Keith Richards look like Johnny Depp.
Now 66, Trejo has played a whole lot of bad guys and criminals in films, and in real life he spent his teenage years in and out of jail and later served time at San Quentin. Now he lectures kids on how crime doesn't pay, but playing the tough guy still comes easily to him. Occasionally, he even gets to do bad things for a good cause - and with Machete, he finally upgrades to his first lead role.
As a Mexican vigilante seeking revenge, he plunges into multiple beheadings and shootings, encounters a nude babe with formidable knife skills while a house burns to the ground around him - all before the opening credits. The lunatic audacity of Machete goes on to include Lindsay Lohan as a nun, Robert De Niro as a drug-dealing, sword-wielding politician and an ingenious but gory escape facilitated by a human intestine.
Trejo may seem intimidating in movies but there is one person who overawes him. He has worked with Robert De Niro three times, including Heat, in which De Niro shot him in the head.
"He is the guy," says Trejo in his slightly accented English. "When Robert De Niro showed up on set, he came up and his first words to me were, 'Don't leave me like this, homes.' That was my line in Heat.
"He said, 'Danny, this is it. This is your starring role. I knew when we did Heat, you had it. You made it, man.' I looked him right in the eyes and said, 'Can I get you some coffee, Mr De Niro?' Billing is not important."
Machete started out as one of the fake movie trailers in the Tarantino/Rodriguez homage to 70s exploitation flicks, Grindhouse, but unlike the Werewolf Women Of The SS or Hobo With A Shotgun segments, the Machete spoof, with its cheerful violence, gratuitous nudity and huge bodycount took on a life of its own. When Trejo and Rodriguez attended the British premiere, a man approached Trejo and lifted his shirt. "He had a huge tattoo of me as Machete on his back, asked me to autograph it and then said he was going to have my signature permanently tattooed. That's when I turned to Robert and said, 'You better make this movie, and you better make it good.'"
Rodriguez and Trejo are cousins, a relationship they only discovered 15 years ago, when Rodriguez was making what would become his breakthrough Western, Desperado, starring Antonio Banderas.
Even then, on location in Mexico, Banderas went unrecognised while the locals flocked to Trejo, assuming he was the film's star.
"They'd seen me in 80 movies," says Trejo, "so people kept coming up and taking pictures with me instead. That's when Robert came up and said, 'I have this idea for this movie. It's called Machete, kind of in the Clint Eastwood-Charles Bronson genre."
Over the years, Rodriguez continued to place Trejo in his movies, including From Dusk Till Dawn, the Spy Kids trilogy and the recent remake of Predators, which Rodriguez produced.
"In each of his movies, you'll notice I'm some sharp object," Trejo points out. "I was Razor Charlie in From Dusk Till Dawn. I was Navajas (Spanish for flick knife] in Desperado, and Cuchillo (another Spanish word for knife] in Predators." In Spy Kids, Trejo's character was even a goodhearted old Uncle "Machete."
"I've heard kids say, 'Oh look, it's Uncle Machete' in about 40 different languages," says Trejo. "And if the kids go crazy but the parents don't know who I am, I say, "Oh yeah, you just let them sit in front of the TV and watch whatever they want."
In the journey from ex-con to icon, Trejo has only had one goal: not to go back. Growing up in various towns throughout Texas and then East LA, Trejo remembers his father being drunk most of the time. He tried dope aged eight, heroin aged 12 and began robbing people aged 14. And he was arrested several times in the course of all this. "I got my high school diploma in San Quentin," he says.
On August 23, 1968, he gave up drugs and alcohol. A year later he left jail, determined to never return. "I knew that the only way I could stay out of prison was to dedicate my life to helping other people," he says. "People who are clean and sober do good things for people and seem to have good lives."
By 1985 he was working as a drug counsellor when one of his former addicts landed a job as an extra on Andrey Konchalovsky's Runaway Train and asked him to come and visit. "This kid said, 'There's a lot of drugs here and I don't want to get loaded,' so I went down to hang out with him, although I'd never been on a movie set in my life."
While he was there, he was offered a job teaching one of the film's leads, Eric Roberts, Julia's brother, how to box.
"When they said they would pay $350 a day, I said, 'How bad do you want this guy beat up?'" he laughs. "They said no, no, no, and told me I had to be real careful because Roberts was highly strung and might really start swinging at me. I said, 'For $350, you can give him a baseball bat.'"
As well as fighting skills, he also taught Roberts how to carry himself like an ex-con, and went on to do the same with the actors of Con Air, especially the leading man Nicolas Cage. "What I showed him was how to stare through a guy. You look, but don't look."
Since his first film 25 years ago, Trejo has appeared in more than 180 films and is refreshingly unluvvy about the business.
"Acting for me is like being a contractor or a plumber or a house painter. A lot of people in the business look at acting as something special. To me, it's just a job."
Trejo makes about ten films a year, and is still happy to accept roles as Criminal, Derelict and Limo Driver. Being stereotyped as a villain doesn't worry him either: "In movies, there's only room for one good guy, but there are always lots of bad guys. I have no problems at all."
And he adds: "When you're in a prison yard and something is going to come down, you really want to be locked up in your cell but instead you have to stand and pretend you're not afraid. That's acting.
"Early in my career a director asked me to kick down a door holding a sawn-off shotgun and hold up 15 people. After the scene, people clapped and said, 'My God, where did you study?' I said, 'Supermarkets. And Bank of America'" v
• Machete is in cinemas nationwide from 26 November
• This article was first published in the Scotland on Sunday on November 7, 2010