The family of a lawyer shot dead in his Chelsea flat during a police siege four months ago will today go to the High Court to complain about the investigation into his death.

Mark Saunders, 32, died of multiple bullet wounds in the head and body when police broke into his flat, ending a five hour armed siege during which he had used a legally-owned shotgun to fire potshots at neighbours and detectives from the window of his £2.2 million apartment in Markham Square.

As the siege unfolded on May 6 this year, the 32-year-old divorce lawyer threw a note - scribbled in marker pen on a shoebox lid - out of the window addressed to his wife, Elizabeth, also a lawyer, suggesting that a row between the couple may have sparked the incident.

In the aftermath, Mr Saunders' family questioned why the barrister was shot when, they say, he was not posing a lethal threat.

They became increasingly unhappy that the Independent Police Complaints Commission delayed more than a week before taking control of the investigation into the shooting.

Today, lawyers for Mr Saunders' sister Charlotte will argue that the IPCC's failure to take over from the Metropolitan police for eight days, and delays in interviewing the police officers involved, breached the European Convention on Human Rights.

Miss Saunders is also seeking a declaration from Mr Justice Underhill that there has been an unlawful failure to disclose sufficient information to her during the investigation.

She argues that the IPCC practice of allowing police officers involved in a fatal shooting to confer with each other, consult documents, delay and then to write up their accounts, is a breach of Article Two of the European Convention on Human Rights - the right to life, and to the use of no more than proportionate force in making an arrest. She says the IPCC has failed to prevent the officers’ evidence from being contaminated.

In a statement she said: “In these circumstances, how can we be assured that the officers’ written statements are an accurate and uninfluenced account of their thought processes when they pulled the trigger.

“I do not understand why not one of the officers who shot Mark has been interviewed by the investigators, four months after his death. I feel this goes against any course of natural justice.

“Members of the general public are interrogated independently and immediately after even minor incidents. Why is it so different for the police, especially when the consequences of these actions are so devastating?

“How can I begin to grieve when I have so many unanswered questions and a dwindling faith in the integrity of the investigation?”

The IPCC practice of allowing officers to confer was agreed with the Association of Chief Police Officers and is contained in the ACPO Manual of Guidance on the Police Use of Firearms.

ACPO, the Metropolitan Police Commissioner Sir Ian Blair, and the Police Federation have all joined the proceedings as interested parties. The hearing is expected to last three days.

Times Recommends

• Gentleman thief stole pages from rare books
• Picture: the Queen in 1970s flares
• Honoured after 70 years: man who saved thousands