STOCKHOLM (Reuters) - Christer Pettersson, the man who may have to stand trial again for the 1986 murder of Swedish prime minister Olof Palme, is a convicted killer with a past of violence, drugs and drink. Pettersson, 50, was found guilty in 1989 of murdering the former prime minister, mainly due to a positive identification by Palme`s widow Lisbet. But an appeals court acquitted him later that year, saying there was not enough evidence. The Swedish state prosecutor`s office said on Friday it had taken the rare step of seeking a retrial against Pettersson for the murder. Palme was killed on February 28, 1986 as he walked home unguarded from a cinema in central Stockholm with his wife. He was shot at point blank range with a heavy calibre bullet that shredded his internal organs. Police say he was probably dead before he hit the icy central Stockholm street, now marked with a bronze paving stone. Pettersson, who was picked up for the shooting almost three years later, has consistently denied committing the murder, claiming he was on his way home after an evening in the city trying to buy amphetamines. Several witnesses, however, said during the first trial that they saw him near the scene of the crime at the time of the shooting. Pettersson`s past paints a picture of arrests, psychiatric care, drug and alcohol abuse and petty crime. Swedish police, who have always believed privately that Pettersson was the killer, have said that the escape route he used that time was the same as that used by Palme`s murderer years later. But despite his past, Pettersson is said to be intelligent and articulate. After he was acquitted of the murder, Pettersson returned home to his modest suburban flat, shunning the police protection he was offered. He spent the first night as a free man drinking and playing cards with friends. Television footage from that evening showed a drunken Pettersson feasting on Vodka and Bailey`s, a cocktail combination later marketed as "The killer" by several Stockholm bars.