By Stuart Ramsay, Chief Correspondent, in Mexico City
A Mexican hitman, who claims to have killed as many as 900 people, has told Sky News how the police and the military are often involved in the planning and execution of his murders.
"Carlos" has been a paid killer for more than 25 years - working for drug cartels, politicians and the military.
We met the hitman in Tepito market - one of the most dangerous places in the whole of Mexico City, despite being at the heart of its smartest district.
The assassin said the network of cartel power is so entrenched in society and powered by so much money that it is unstoppable.
"On some occasions, we have to go to places where weapons are not allowed and then they (police) meet us.
"They take us to a hotel and they provide all the weapons that we may need, money and everything so that one can do the job one has to do."
The abduction of 43 students last September has forced Mexico into confronting its crime problems.
Carlos believes that the students are already dead, and uses a chilling example from his own experience to explain why he is so certain.
"Let me tell you a story. Some protestors came. We let them in and then we closed the road, we closed the entrance, we closed the exit. When they were stuck in the middle we killed them all," he recounted.
"Then a (rubbish) truck from the army came and collected them all. Then street sweeper machines went past. They opened the road again, as if nothing had happened.
"The students are dead, it is more convenient. For kidnapping you get 160 years, for killing its 35. It's a huge difference, don't you think?"
Mexico is described by many as a "Narco State", where government and civil society appear powerless against drug money, cartels, corruption and terrible violence - committed on an almost daily basis.
This country bordering the United States and Central America has become a transit point for drugs across the world.
The revenues are mind-blowing - tens of billions of dollars a year.
The demand for what it can deliver to affluent societies is insatiable.
It is the root of the problem of course, and widespread poverty, combined with the need to make a living, are the crumbling foundations of a state teetering on the edge of disaster.
Mexico is in trouble. It is failing. A black market culture where anything can be bought is all-pervading. Nobody is above this. Absolutely nobody.
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Gallery: Mexico's Drug Cartels
