Katharine Walker reports.
Christopher Alder collapsed and died at Queens Gardens police station in April 1998.
Since his death, his sister Janet has fought tirelessly to find the truth behind her brother's death and the events afterwards which saw him lie in a mortuary when his family thought he'd been buried.
In 2011 his body was discovered in a mortuary and it emerged a 77-year-old Nigerian woman, Grace Kamara, was buried in his place at Hull's Northern Cemetery.
In the wake of George Floyd's killing, Christopher's sister Janet is campaigning for more to be done to tackle systemic racism in the police.
Her appeal comes as a new report shows that 65% of people from minority backgrounds feel that the police are prejudiced.
Christopher Alder's death in a Hull police station made headlines, when CCTV showed him gasping for air as officers joked around him.
It took 11 minutes for him to stop breathing and as he lay dead, monkey-like noises were heard on the audio tape.
An inquest ruled he was unlawfully killed, but five police officers who stood trial for his manslaughter were acquitted by a judge.
In 2011 his body was found in the mortuary at Hull Royal Infirmary, eleven years after the Alder family thought they'd buried him.
A new survey from the charity Hope Not Hate found that 65% of ethnic minority communities feel that the police were biased against people from their background.