The family of Jean Charles de Menezes will learn the outcome of a court challenge over the decision not to bring charges over his death.
Relatives of the Brazilian took their case to the European Court of Human Rights (ECHR) last year - almost a decade after he was mistaken for a suicide bomber and shot dead by police marksmen on a London Tube train.
Lawyers for the family argue the assessment used by prosecutors in deciding that no individual should be charged over the shooting is incompatible with Article 2 of the European Convention on Human Rights, which covers the right to life.
The claim also challenged the definition of self-defence.
Mr de Menezes, 27, was shot dead by Metropolitan Police firearms officers at Stockwell Underground station in south London on July 22 2005.The following year the CPS announced that no individual should be charged.
In 2007 the Met was fined £175,000 after being convicted of breaching health and safety laws.
An inquest jury later rejected the police account of the shooting and returned an open verdict. The coroner had already ruled out a verdict of unlawful killing.
In 2009, the family of the electrician agreed an undisclosed settlement with Scotland Yard.
A hearing was held in the case was held in the ECHR's Grand Chamber in June, more than seven years after the original application was lodged. The judgment will be delivered on Wednesday afternoon.