A police officer driving a van who followed two teenagers before they both died in an e-bike crash in Cardiff will not face criminal charges, the Crown Prosecution Service (CPS) has said.
The CPS said there was insufficient evidence to provide a realistic prospect of conviction.
The driver of the police van, along with another officer in the vehicle, had previously been served with gross misconduct notices.
The deaths of Kyrees Sullivan, 16, and Harvey Evans, 15, sparked a riot in the city's Ely suburb.
On Monday, Malcolm McHaffie, head of the Crown Prosecution Service Special Crime Division, said: "Following a thorough and detailed review of the evidence in relation to a single allegation of dangerous driving in this case, we have decided that no criminal charges will be brought against a South Wales Police officer.
"We have concluded that there is insufficient evidence to provide a realistic prospect of conviction."
The CPS added in its statement that it fully understood that this would be "disappointing news for the families of both boys" and would offer a meeting with them to explain their reasoning further.
Following the deaths, rumours rapidly spread on social media that the boys had been chased by police before the crash.
South Wales Police later said that its officers had been following the boys in the minutes before, and the force referred itself to the police watchdog.
Cars were set alight and fireworks thrown at police after 100 to 150 people gathered in Ely on 22 May, 2023, the evening of the crash.