Four years ago, the Colombian government implemented a controversial law that laid down the terms for a peace process with the country's paramilitary groups. The following questions and answers discuss the impact of the peace deal and why it has raised controversy.

WHO ARE COLOMBIA'S PARAMILITARIES?

The paramilitaries were initially small vigilante groups of armed thugs founded in the early 1980s by large landowners and cattle ranchers to protect themselves from extortion and kidnapping by leftist guerrilla groups.

In 1997, these groups unified to form a loose umbrella organisation - the United Self-Defence Forces of Colombia (AUC). Its aim was to destroy Colombia's two main guerrilla groups, the Revolutionary Armed Forces of Colombia, FARC, and the smaller National Liberation Army, ELN. The right-wing paramilitaries were heavily involved in the drug trade. By the mid-1990s, they controlled major smuggling routes and shipped tonnes of cocaine to the United States by sea.

By early 2000, the AUC had grown into a nationwide force, with strongholds in northern Colombia, and a major player in the country's 45-year-old conflict. Its death squads went on the rampage, imposing a rule of terror over civilians. In 2001, the U.S. State Department designated the AUC as terrorists.

WHAT IS THE PEACE DEAL?

In December 2002, the AUC declared a ceasefire that started an arduous peace process with the government of Alvaro Uribe, culminating in the Justice and Peace Law. The controversial law sets out a framework for negotiating peace with the paramilitaries and their demobilisation. The law gives incentives for fighters to lay down their arms, offering reduced jail terms for warlords (from five to a maximum of eight years). In exchange, paramilitary chiefs must confess all their crimes, give details of massacres, handover stolen property and land, and reveal the whereabouts of mass graves.The government says the law allows paramilitary victims to seek justice, receive compensation and discover the truth about what happened to their murdered relatives.

Since 2003, over 31,000 paramilitary fighters have laid down their arms in high-profile demobilization ceremonies across the country. This is seen as a first crucial step towards reconciliation between the paramilitaries and their victims.

A handful of paramilitary chiefs, though, have refused to take part in the peace process and continue to command criminal gangs. Over thirty paramilitary chiefs are serving prison sentences in Colombian jails, while fifteen have been extradited to the U.S on drug trafficking charges.

Ongoing criminal trials of paramilitary commanders are taking place in U.S. and Colombian courts. So far, the paramilitaries have confessed to over 6,500 murders, and nearly 1,000 disappearances. They have also accused the government of actively conspiring with them, and have implicated dozens of senior army officials, and over 200 politicians, including 120 mayors and 26 senators. Dozens of Colombian lawmakers are in jail for conspiring with paramilitary groups, many charged with election fraud. WHY IS THE PEACE PROCESS SO CONTROVERSIAL?

Rights groups have heavily criticised the Justice and Peace Law. They argue paramilitary chiefs guilty of widespread human rights abuses are serving only token jail sentences, while hundreds of mid-level commanders and foot soldiers have not been punished for war crimes they committed.The demobilisation of paramilitary groups has not guaranteed the dismantling of their criminal structures. Across the country, over 2,300 killings have been attributed to the paramilitaries since their declared ceasefire seven years ago, says Amnesty International.

Demobilised combatants are being "recycled" into the conflict, rights groups say, and have found work with drug barons or have formed their own new criminal gangs.Recently, the Colombian government started to hand out financial payments to victims of paramilitary violence. Government forensic teams have exhumed over 1,000 bodies and have handed the remains to relatives of paramilitary victims.

But many victims have received few, if any, reparations. Vast swathes of land snatched by the paramilitaries has yet to be returned to their rightful owners.

The extradition of paramilitary warlords to the U.S has also raised concerns. Critics argue that because the U.S courts are trying the warlords for drug trafficking and not atrocities they committed, they have little incentive to confess their war crimes. In April, a U.S court sentenced paramilitary boss 'Don Berna' to 31 years in jail for exporting cocaine but little was revealed about the true scale of the atrocities he committed.

WHAT ROLE HAVE THE PARAMILIATRIES PLAYED IN COLOMBIA'S HUMANITARIAN CRISIS?

The paramilitaries have been responsible for some of Colombia's worst human rights atrocities, killing scores of trade unionists and farmers and others they suspected of collaborating with guerrilla groups.

Paramilitary violence over the decades has directly forced thousands of civilians to flee their homes.

The number of people uprooted by paramilitary threats and violence is unclear and figures vary, with the paramilitaries accounting for about 15 to 35 per cent of the roughly 3.5 million displaced people in Colombia.

HAS SECURITY IMPROVED FOLLOWING THE DEMOBILIZATION OF PARAMILITARY GROUPS?

Government figures show a significant fall in violent crime and kidnapping. But to what extent this is attributed to the demobilization of paramilitaries is difficult to measure.

While the lucrative cocaine trade fuels the coffers of armed groups, including those run by former paramilitary combatants, violence and displacement will continue as a myriad of criminal gangs fight over the control of drug smuggling routes and coca production.

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