Aamer Anwar said officers “closed ranks” following the death of Sheku Bayoh in Kirkcaldy, Fife, on 3 May last year.
The 31-year-old father-of-two died after being restrained by officers responding to calls of a man with a knife.
The Police Investigations and Review Commissioner (Pirc), Kate Frame, is currently investigating the incident, with a report expected to be sent to the Crown Office in the coming weeks.
In a statement yesterday, Mr Anwar said: “Over the course of the last year the Bayohs have met families who also lost their loved ones at the hands of the police. They told the Bayohs that there is something deeply shameful about a system where people are unlawfully killed at the hands of our protectors, yet the perpetrators remain free.
“As we have seen from Hillsborough, it is instinctive for police officers to blame the dead rather than their own and for families to be placed in the perverse situation of relying on the police for the truth.”
Mr Anwar said the press had been “manipulated” to portray Mr Bayoh as “drug-crazed” and “knife-wielding”.
And he said the family’s confidence in the Pirc was “shattered”.
Lord Advocate Frank Mulholland has confirmed a fatal accident inquiry will be carried out into Mr Bayoh’s death.
Responding to Mr Anwar’s comments yesterday, Brian Docherty, chairman of the Scottish Police Federation, said: “The federation looks forward to as early a fatal accident inquiry as is possible in order that the full circumstances surrounding the death of Mr Bayoh can be examined.”
A spokesman for the Pirc said: “The commissioner recognises the tragic circumstances in which Sheku Bayoh died and her investigation is committed to getting to the truth of what happened.
“The inquiry remains ongoing, and the commissioner is committed to delivering a thorough, impartial and independent investigation. A further report of our findings will be submitted to [the Lord Advocate] in due course.”