After stabbing Nowak, who came from Chafford Hundred in Essex, Digwa lied to police that he was the victim of a racist attack.
The case later sparked protests after police body-worn footage was released showing officers failing to give Nowak first aid and instead handcuffing him as he lay dying, despite him telling officers he could not breathe.
The Independent Office for Police Conduct previously said it was investigating two officers for potential gross misconduct.
Twelve police officers and a police dog were injured during the protests in Southampton on 2 June.
Demonstrators gathered outside the city centre police station before moving to an area near the Digwa family home and the murder scene.
More than 30 people have so far been charged with violent disorder following the incident.
On 15 June, former Solicitor General Ellie Reeves KC referred the case to the Court of Appeal under the Unduly Lenient Sentence scheme.
Sikh leaders have reported a “backlash” and increase in “hate crime” against their community following the case.
