Four senior police officers are under investigation over claims that evidence in a murder trial was withheld from the prosecution and court. One is in charge of ethics for the Association of Chief Police Officers (Acpo) and all hold high-ranking positions in three forces in England. The allegations concern an inquiry by Staffordshire Police ? where the four previously worked ? into a 2002 gangland killing. It led to the conviction in 2008 of five men, who received sentences totalling a minimum of 135 years, for the murder of Kevin Nunes, a footballer shot dead after becoming involved in a drugs feud. Mr Nunes, 20, who had been on the books of Tottenham Hotspur, was killed in a country lane in Staffordshire. He had been selling drugs, reducing the profits of rival dealers. His killers were convicted after a two-month trial at Leicester Crown Court. The investigation into the officers, which is being overseen by the Independent Police Complaints Commission (IPCC), is a response to claims that material and evidence that could have affected the trial were withheld. The allegations being explored include conspiracy to pervert the course of justice and misconduct in public office. Those being investigated include Adrian Lee, the Chief Constable of Northamptonshire Police and head of police ethics at Acpo. Also under scrutiny are Suzette Davenport, his deputy in Northamptonshire, Jane Sawyers, an assistant chief constable in Staffordshire, and Marcus Beale, an assistant chief constable with West Midlands Police. In all, nine officers have been told that they are under investigation, although this does not imply any wrongdoing. The senior officers have not been suspended or arrested but have been served with official notices about the investigation. The Guardian reports today that the inquiry was triggered by a challenge in the Court of Appeal by the men convicted of Mr Nunes?s murder. The court asked the Criminal Cases Review Commission (CCRC) to investigate the disclosure of evidence in the original trial. Material uncovered by the CCRC was referred to the IPCC, leading it to open the new investigation. The IPCC said: ?We can confirm the Independent Police Complaints Commission is managing an investigation into allegations against a number of former and serving Staffordshire Police officers. The investigation is being carried out by the Chief Constable of Derbyshire, Mick Creedon, under the direction of the IPCC.?