Metropolitan police reopen inquiry into death of Kester David Police investigating the death of an African-Caribbean man found burned alive failed to interview vital witnesses for more than a year, despite them contacting officers within hours to report their suspicions, the Guardian has learned. Officers concluded the death of Kester David in July 2010 in north London was suicide without interviewing a witness who told of hearing screams of fear and another witness who was suspicious at seeing two white men near the scene. Scotland Yard on Wednesday dropped its insistence that David had committed suicide and launched a fresh inquiry amid family claims that he was murdered. An internal police report found a "catalogue of errors" in the investigation after David, 53, was found dead in railway arches at Palmers Green station. Potentially vital witnesses had not been interviewed while the family of David believed police failed them because of the colour of their skin, and had been disrespectful and insensitive. After 18 months of telling the family David doused himself in petrol before setting himself alight, the Met now says the death is "unexplained" and will be investigated by the Homicide and Serious Crime Command, led by Detective Chief Inspector Steven Lawrence. The family of David, a bus driver, never believed the police account. Their suspicions were stoked when they were passed a copy of the internal police review, which exposed a string of failings and errors. At the inquest a coroner recorded an open verdict. According to the Met's report, which the Guardian has seen, one day after the death a witness contacted police to say they heard screams at the time of David's death. The witness was not interviewed for more than a year. In a statement, the witness said the screams heard at about 4.20am were of a man in fear, shouting at someone not to do something: "I suddenly heard the word 'No' shouted by a male at the top of his voice in a panicked and frightened way, as if he was shouting at someone else not to do something. I then heard a second 'No', shouted only five or six seconds afterwards. The second shout was almost identical to the first in that it was a frightened, panicked shout directed to someone who was about to do something against their will ... it was a shout of fear of pain. Another witness, again not interviewed for a year after the death, said he had seen two white men near the scene at the time of the death. He reported it to the police the day after, because it was unusual for people to be in the arches at night. David's mother, Winifred Griffith, said she expected police to now carry out a full murder investigation. We are disappointed that it has taken so long and that it has only been opened following our representations rather than as an immediate response to the findings of internal investigation reports that were available to senior police officers several months ago. We would not have had to wait so long and fight so hard if Kester had been a white man. In her formal complaint about the case, Griffith said: "I feel that the police jumped to a number of conclusions, which were not supported by the evidence. The family and I feel that all these shortcomings and inconsistencies should have been enough to require the police to carry out further investigations beyond their initial conclusion of suicide. The police made too many assumptions and could not explain lots of inconsistencies. In her complaint, Mrs Griffith said: "The police did not treat us with respect and dignity, and did not seem to care about what we thought. They also gave us incorrect information at times. The case of David has strong parallels to the 1997 case of Michael Menson, who was found in Edmonton, north London. Police said Michael, who had suffered horrific burns, had tried to kill himself. Two years later, after police changed their approach, one man was found guilty of murder and another of manslaughter. After the Menson convictions, then Commander Cressida Dick said: "What happened when Michael was murdered would not happen today, it would be a very different investigation today." In a statement, the Met said: "A post-mortem examination gave cause of death as burns and inhalation of fumes. Enfield borough police investigated the case and concluded the death was non-suspicious. Following concerns from Mr David's family, two reviews into the investigation were carried out by senior officers from Enfield borough in September 2011 and January 2012. The results of those reviews remain under consideration and detectives from the Homicide and Serious Crime Command are to reinvestigate.