Francisco Tejeda is 56 years old. He hails from Colima, western Mexico and has completed 23 of a 40 year prison sentence.
Paco, as he is known, is behind bars in Mexico City's Norte prison for his part in the illegal activities of the Guadalajara cartel, under the leadership of Rafael Caro Quintero. He is also one of the accused in the murder of DEA operative Enrique Camarena Salazar in 1985.
He developed his aptitude as an inventor and painter while in the penitentiary and now runs a painting workshop which has turned out a number of professional artists.
Here he tells us about his life in the world of drug trafficking.
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From BBC News
"We didn't have enemies"
"I wanted to be a policeman, and one day I saw an ad in a newspaper looking for recruits to an academy. Well, that was it for me ... I took my brother, the youngest one, and another friend ... and of the 40 lads who formed that first generation of Tijuana police officers, 39 are dead. I'm the only one left. And I survived because I'm in here. All the others were shot.
When I went into the force, I started to become corrupt. Little by little, you get into it ... First you want to do your job well, but your colleagues pull you in and you become corrupt yourself with no solid moral values ... I ended up mixing with narcos.
My parents were always good role models. I ask myself why I went bad. How come a police officer starts out honest and ends up corrupt ... you start out taking money from the criminal and before you know it you are helping him, talking to him ...
Policing is fascinating. I loved it ... not any more, but I did once. The adrenalin rush ... I think that´s why it appeals so much to youngsters, who go into it for the thrill. The films and television and all the trappings, it gets to you.
That's what happened to me when I first started. When I still thought the criminals were the bad guys and I said to myself 'how can I (as a police officer) think of dealing drugs?' Until one day, it happened ...
Being a policeman is just one disappointment after another. The Commander asked us for money, and you had to pay up. If you didn't your punishment was guarding the money exchange houses ... we were corrupt, that's all there is to it. Not nice eh? I don't really like talking about it.
It's amazing to see the children of my original work colleagues, now as the bosses. Generations and generations have been involved in this. There's a lot of money in it, and while the police force remains corrupt, it will just go on and on and nobody can stop it.
It's an amazing thing, corruption. All anybody thinks about is money, stealing it, just getting your hands on it ... and I made the mistake of getting in with these people.
And they caught me with them. We didn't have enemies: when I was into all of that, there were five or six narcos, all friends.
Now there are 20, 30 and ... they aren't all friends. They go about killing each other, to achieve more power. The narco is a very greedy person.
I never knew what it was to have a family life. Out there, I just never had it. I'm ashamed to say it. OK, I had my wife, my children and I brought money into the house. But then I went out again, my mind totally on my job. It's in here that I discovered the love for family, for my children, love of myself, my self respect ... all this I discovered here in prison.
I wouldn't really like to discuss my life and drug trafficking because I don't want to excuse the crime. There was so much damage done, that´s why they gave us so much television coverage when they were looking for us for the Camarena business (murder of the DEA agent).
And they really exaggerated how rich Rafael was (Rafael Caro Quintero, Guadalajara cartel boss) ... They said he had made so much money, that he wanted to pay of the country's debt! None of this was true."
"People risk everything for money"
"I risked my life in such a cavalier way. I could have been killed many a time ... Going about risking your life for money, for stupid things, thinking you're the bees' knees. People think it´s very clever to go around wearing a gold watch or having a big car, or a gun. It´s all so silly, so stupid.
These people risk everything for money, but then once they have it ... I saw people amass millions of dollars, then they didn´t know what to do and ended up in despair.
I'll bet you there are hundreds of people like that, they've got millions stashed away under the mattress or somewhere and they can´t even spend it.
Two of my brothers were shot dead, and I lost a brother-in-law six months ago, shot dead on his own doorstep.
Children are being killed on the streets. It's a dirty war ... narcos going about killing each other. Remember in Colombia, the bombings? Well, it´s the same here now. Feuds between narcos.
I'd very much like you to observe my experience - going from criminal to artist. To discover what it's like to study, to know that you can change. Look at me: a decent man who turned into a drug trafficker, and back to a decent man again.
Where do you find happiness? Well not in money, that's for sure. In here, I discovered that it's the simple things in life. Being happy with a watch that shows you the time, not one that you show off with.
As far as I'm concerned, Rafael Caro Quintero and all those others are neither friends nor enemies. That´s it. Do you think I want any more trouble in my life? After so many years in prison, I don´t need very much money to live on.
I've sold paintings for 20,000 pesos (US$840). Pictures I have painted in one day! In other words, I live very well from my painting. It's been hard but I've achieved it here in prison.
You feel the need to express yourself ... there are lots of things you express unwittingly, your unconscious can betray you and can make you say things that sometimes you don´t mean. But it comes across in the paintings.
I have been approached to write a novel and make a film but I refused. I said: 'No, what shall we do? Another Scarface?' And we'd probably do it better! But, what would be the point? What would we gain? People would go and see the film and you would teach them to how to become drug traffickers!"
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Francisco Tejeda talked to BBC Mundo from Mexico City´s Norte prison.