Two Hampshire officers are under investigation after body-camera footage showed 18-year-old Henry Nowak handcuffed and arrested in Southampton while saying he had been stabbed and could not breathe.
The police watchdog said the officers may have breached standards on duties, use of force and discreditable conduct, and is also examining whether race or religion influenced their decisions.
Vickrum Digwa, 23, had falsely told officers he was the victim of a racist assault by Nowak before he was convicted of murder and sentenced last month to at least 21 years in prison.
Nowak's death has fueled claims by far-right activists and politicians of bias against white people in the justice system, and violence broke out in Southampton after Digwa's conviction.