Miguel doesn't sleep well these days. It's not his conscience - in his view, it was quite reasonable to kill the man who shot him in the head.
"I was taught to return a favour," he says. "It was a small sin."
Miguel is not his real name, but the one he has chosen for the purposes of interview. He wants to be filmed in shadow, which is a shame because it means we cannot show how his brow is distorted by an acute dent in the left temple where the bullet entered, and a wider, shallow one where it exited on the right. He says he was shot by a member of a rival drug cartel, who was owed US$250,000 by Miguel's boss. After 32 days in a coma, Miguel emerged to take his revenge.
His restless nights are the product of a more general anxiety. Now might be a good time to retire, he thinks, but it's hard to change career at this stage because if your enemies don't get you, then your friends will.
"You can change your phone number but your friends know how to find you," he says. "I can't let them down, because we're the same, we're family and you have to respect your family."
Miguel lives in Culiacán, the capital of Sinaloa, the state at the centre of Mexico's spiralling drug wars. In early December, the bodies of 13 men turned up at the side of a country road, their hands tied with rope, gunshots in the head and the back. They are believed to have worked for one of the drug cartels whose turf war is tearing Mexico apart. Such killings are an everyday occurrence all over the country, most commonly along the drug routes leading to the US border.
In the past year, nearly 5,400 people have been killed in drug-related murders, more than doubling the previous year's total. Many were de capitated. Others had their tongues cut out. The cartels, which have been weakened by war, are now turning to kidnap, extortion and other forms of organised crime.
"The spiral of violence is a sign of ungovernability which may lead to anarchy," admitted President Felipe Calderón in early December. American pundits have warned that Mexico may become a failed state.
For 70 years, Mexico was governed by the Partido Revolucionario Institucional, the PRI, which accommodated the drug business. Politicians were paid, drug traffickers plied their trade and violence remained under control. But when Calderón came to power in 2006, he decided to take on the cartels, which were growing more powerful as they were squeezed out of Colombia and pushed north.
"Calderón poked a hornet's nest with a big stick, but he made no preparations for the consequences," says Mario ópez Valdez, a PRI senator for Sinaloa. "Now the angry hornets are out, but no one's wearing protective clothing."
José - again, a pseudonym - drives around Tierra Blanca, the middle-class residential area of Culiacán where the drug traffickers used to live. He likes to show off his huge 4x4 Chevrolet Avalanche, which he drives while drinking beer and talking on the mobile phone to a string of girlfriends. Apparently high on cocaine, he talks at machine-gun pace in narco-slang, somewhat alarmingly taking his hands off the wheel to point out the sights to visitors.
"That's where El Mochomo was betrayed," he says, indicating a house where one of the most famous drug traffickers, Alfredo Beltrán Leyva, was arrested in January. Graffiti on the garage door reads: "I love you, Mochomo, I miss you, your girl loves you."
José and Miguel work for the Sinaloa cartel, members of which are believed to have turned Beltrán Leyva over to the authorities as they battled to gain new and more profitable trafficking routes. In response, the Beltrán Leyva cartel murdered the son of the Sinaloa cartel's fugitive leader, Joaquín Guzmán, known as El Chapo, which translates as "Shorty".
"That was when the war began," says José. He is sorry to see the streets so quiet, after years in which they pulsated with luxury vehicles and extravagant parties. Many houses are empty, their drug-trafficker owners having quietly removed themselves to the countryside, where they are less likely to be killed.
At the shrine to Jesús Malverde, patron saint of drug traffickers, a trio of guitar, harmonica and singer are playing a narcocorrido, a praise-song to the drug cartels. As drugs are the foundation of Culiacán's wealth, and the present war is bad for business, it is a lament:
Tierra Blanca, you seem so sad now.
Your streets are deserted,
No longer humming with the latest cars,
Nor with the roar of the machine-gun.
Jesús Malverde is a Robin Hood-type figure, a bandit who was hanged by the Mexican authorities in 1909. Once a simple folk hero, he is now worshipped by those who have become rich on narco-profits. At his shrine, plaques in the name of the Beltrán Leyva family, among others, bear legends such as: "Thank you for safeguarding our journey from Sinaloa to California."
Drugs are now deeply embedded in Mexican culture, while corruption runs through the bureaucracy and the security forces. As the violence increases, President-elect Barack Obama may find that he has to deal with war not just far away in Iraq and Afghanistan, but right on his border.
Lindsey Hilsum is international editor for Channel 4 News