More than a dozen defendants have entered their pleas in connection with the riots in Ely, Cardiff, last year.
The alleged disorder followed the deaths of two teenagers in an e-bike crash.
Harvey Evans, 15, and Kyrees Sullivan, 16, died in the collision. Police said no other vehicles were involved.
CCTV captured a South Wales Police van appearing to follow the teenagers minutes before the crash.
The force then referred itself to the Independent Office for Police Conduct (IOPC), the police watchdog.
The crash happened on Snowden Road at around 6pm on 22 May, and a total of 31 people have been charged in connection with the disorder that followed.
Nineteen people appeared at Cardiff Crown Court on Monday.
Kyle Telemaque, 19, from Ely, pleaded guilty to the charge of riot and two counts relating to the supply of cannabis.
Jumana Fouad, 18, from Ely, pleaded guilty to the charge of riot.
Callum O'Sullivan, 23, of Ely, appeared before the court but did not enter a plea.
Lianna Tucker, 18, from Ely, Michaela Gonzalez, 26, from Ely, Jayden Westcott, 20, from Ely, and Jamie Jones, 23, from Llanrumney, were the first group of defendants to plead not guilty to riot.
Luke Williams, 31, of Ely, Connor O'Sullivan, 25, of Caerau, Zayne Farrugia, 24, of Caerau, Lee Robinson, 27, and Jaydan Baston, 20, of Caerau, also pleaded not guilty to the charge.
McKenzie Danks, 21, from Caerau, denied a charge of riot, but admitted two charges of assaulting an emergency worker, namely police officers.
McKenzie Pring, 19, from Caerau, Jordan Webster, 28, from Ely, Jordan Bratcher, 26, from Llanishen, Ashdon O'Dare, 26, from Ely, Keiron Beccano, 25, from Ely, and Harvey James, 18, from Fairwater, were the last group of defendants to appear before the court and all six entered pleas of not guilty to the charge of riot.
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Recorder of Cardiff Judge Lloyd-Clarke did not set a trial date and the case was adjourned until the next hearing on 1 November.
All 19 defendants were granted unconditional bail.
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