Chris McCall, Jakarta – They catch the thief, beat him, often burn him alive. When the police arrive they find a corpse and no one knows who the killers are.

Jakarta's police are struggling to control a wave of vigilante killings like this. Some 40 presumed criminals have been killed in this way this year in the Indonesian capital, usually before police make it to the scene. More than 30 others have been lucky to escape with their lives. And the problem is not confined to the capital.

Legal experts say it shows that Indonesians just do not trust their police. It usually happens in Jakarta's ugly slums or other poor districts, often over a stolen motorcycle. In a country whose common people are lucky to earn 250,000 rupiah (HK$250) a month, such a machine is very much something to kill for.

Jakarta police spokesman Lieutenant-Colonel Zainuri Lubis says the force wants to stop the vigilantes, but its men cannot be everywhere. He blames the economic collapse, which has hit the poorest sectors of Indonesia's society hardest. Millions have been thrown out of work.

"The Jakarta police is very concerned and regrets these cases, although there is a positive aspect in that the public are fighting crime," he said. "This issue makes people angry because many of the victims [of theft] are also poor, like drivers of motorcycles or taxis, shoppers, and so on."

On May 10 in the southern suburb of Pondok Gede, four men were spotted entering a yard to steal a motorcycle. The owner saw them and yelled for help. He got it. According to a police report, a mob attacked the four men, caught them and set them on fire. When police finally arrived, only one could be identified.

On May 14, a man from Sumatra named as Kaharuddin, 33, was caught and burned alive in the suburb of Tangerang. He had been spotted riding a motorcycle that had gone missing three days earlier. Police arrived too late to save him.

Doling out rough justice is often far easier in Indonesia than trying to get redress through its notoriously corrupt legal system. Patra Zen, of the Indonesian Legal Aid Foundation, said 27 such killings had been reported this year just in Lampung province on the southern tip of Sumatra, a rural area, where many of the cases involve thefts of animals.

There are many such cases elsewhere too, he said. "There is a problem of implementation in the legal system," Mr Zen said. "The police cannot sort these problems out properly."

The police probably have their own past to blame, he said. Under former president Suharto they were very much seen as the junior partner of the military, and were officially classified as part of it.

Although the police force regained its independence last year, it retains many quasi-military features, including military ranks and often the use of military-style uniforms and weapons. Police officers have also been implicated in past human rights abuses. "Before, the police also carried out violence. The people don't trust them," Mr Zen said.