Wall of silence
Suspicious death , Issue 1644 SHEILA BLANCO had spent almost 17 years and £150,000 investigating the suspicious death of her son, Mark, at a 2006 gathering attended by drug-addled singer Pete Doherty when a Channel 4 documentary looked set to finally blow the case open.

The film, Pete Doherty, Who Killed My Son?, presented compelling fresh evidence that appeared to support Sheila's belief he had been murdered.

However, two years later, Scotland Yard refuses to investigate the new leads. Now Mark's family has submitted a complaint asking whether the Met's continuing lack of engagement is down to apathy, incompetence or corruption.

Hurried exit
The Libertines and Babyshambles frontman, whose notorious benders and arrests made him a tabloid regular, was captured on CCTV running past Mark's body in the street and fleeing the scene with his girlfriend Kate Russell-Pavier and bodyguard, Johnny "Headlock" Jeannevol.

Minutes earlier, Doherty, Jeannevol and Paul Roundhill, the drug-dealer tenant of the East End flat where they had been partying, had scrapped with Mark and physically removed him on Doherty's instructions.

Sheila said: "Mark didn't fit in with that crowd. He went in buzzing about the new play he was in and disturbed Doherty's space. They were all drugged up and Mark wasn't. They attacked Mark and Doherty gave the command for Headlock, his attack dog, to throw him out."

The Cambridge-educated aspiring playwright and actor, who would have turned 49 this week, returned two minutes later, then mysteriously plunged from a stairwell balcony, suffering fatal head injuries.

Officers appeared to assume it was a suicide, making no effort to seal the potential crime scene or protect evidence. One officer callously handed Sheila a lens from Mark's broken glasses to "keep as a souvenir". She says the force has wilfully resisted all opportunities to find out what really happened that night.

Forensic investigation
The Channel 4 filmmakers spent three years interviewing key witnesses and employed forensic scientists to re-examine the CCTV footage using new techniques. The original Met expert was more used to investigating car crashes.

FBI trainer Grant Frederick said the evidence was consistent with Mark being thrown or dropped. He was able to make out a second figure on the balcony and an arm stretched out as Mark tumbled free of the railing.

Forensic video analyst John Kennedy told the programme he believed Mark was unconscious when he fell because he made no effort to protect himself from injury.

Added to the 2007 coroner's verdict, which "unreservedly" ruled out suicide and asked the Met to reopen the case, Sheila was convinced that they finally had enough to force the police to step up.

"It presented such an irrefutable case that Mark had been murdered, we were sure that the Met could no longer resist a full and proper investigation," she told the Eye. "What more could they need?"

However, she and her family were met with a wall of silence and later learned their liaison officer of three years had retired without even notifying them. No replacement had been assigned.

Fresh complaint
Now their solicitor Mike Schwarz has submitted a new complaint to the Independent Office for Police Conduct (IOPC), asking it to look into the possible reasons that so many opportunities to further the investigation were missed or ignored, including corruption, collusion, protection of informers or plain negligence, and to hand the investigation to a new team.

"Everyone who watched the documentary has come to the same conclusion. So why are police so reluctant to even test the evidence?" Sheila said. "They hide behind the phrase 'Our investigation is ongoing', meaning they can't share any details." The film also sees one of the witnesses to the altercation, Naomi Wang, tearfully insist that Mark's death must have been manslaughter or murder.

Jeannevol describes the police's total lack of interest when he walked into a station and confessed to killing Mark three weeks later. Officers dismissed him as mentally ill, even though he was declared to be of sound mind when he told them: "I murdered Mark Blanco."

Jeannevol, who had a history of violence, told Channel 4 he changed his mind because he realised he had "opened a can of worms" and the fuss was dying down. He withdrew his confession. Notes from his interview were lost.

The film alleged that he went on to brag, confess or hint at his involvement to six other people, yet none has been asked to give a statement.

Jeannevol continues to deny murdering Mark, and Doherty has always insisted he has no knowledge of how he fell to his death.

Cruel refusal
Owen Phillips, executive producer of Pete Doherty, Who Killed My Son?, said: "The evidence is compelling. It remains a mystery why the Met continues to be to be reluctant to even interrogate the evidence or witnesses. Why haven't they gone back to Naomi and Roundhill? Grant Fredericks trained FBI officers in forensics and testified in hundreds of trials. Why not at least speak to him?... Their refusal to engage with Sheila has been cruel."

A Met spokesperson told the Eye: "There is no update on the investigation – it is ongoing." The words Sheila hears in her sleep.