Last Sunday afternoon a homeless mother-of-five left her hotel room in Middlesbrough to nip to a nearby shop. On her way, 34-year-old Stacey Vint bumped into some locals she knew and joined them on their way to what had been described on social media as a “pro-British” protest in the town centre.

Five days later, she found herself being handed a 20-month prison sentence for violent disorder after becoming part of a 1,000-strong riot that saw police attacked as homes, cars and public buildings were vandalised.

A barrister representing Vint, who had drunk alcohol and smoked cannabis on the day, told Teesside crown court that her involvement was “simple”.

“One of the group she was with asked her to give him a hand with a wheelie bin, which had been set on fire, and she did,” Andrew Turton said. “Stupidly, she took hold of the bin, pushed it towards police, and fell at their feet.”

A 10-second video of the incident, which had already gone viral amid ridicule on social media, showed Vint and an unidentified man wheel the burning bin towards a line of officers, before it slid out of control and dragged her to the ground.

The smashed windows at Teesside crown court were still boarded up as the judge, Francis Laird KC, sentenced Vint, telling her the “large-scale act of public disorder” had caused significant physical and financial damage to her home town, traumatised police officers and terrified residents.

The judge found that Vint had no racist or ideological motivation for her offence, but that her sentence had to be increased because of the riot’s scale, impact and the “backdrop of other violent incidents” across the country.

The court heard that Vint’s life had been blighted by drug and alcohol abuse and domestic violence, and that she had become homeless after fleeing an abusive relationship and seeing all five of her children taken into care.

As Vint sat impassively in the dock, wearing a grey prison tracksuit, Turton said she had “expressed shame and regret” and “understood the need for the court to impose deterrent sentences”.

Such sentences were being handed out at remarkable speed at courts across England and Wales on Friday, with Vint just one of more than 300 people so far charged with offences linked to violent protests and riots that broke out following the killing of three young girls in Southport on 29 July. Initially fuelled by false online claims that the perpetrator was a Muslim small-boat migrant, far-right influencers and conspiracy theorists called for people to take to the streets and amplified planned protests in dozens of towns and cities.

Although the misinformation was debunked within a day, demonstrations advertised on multiple social media platforms under vague slogans including “enough is enough”, “save our kids” and “protect our country” became a vehicle for wider anti-Muslim, racist and xenophobic rage.

But at Teesside crown court on Friday, there was little exploration of rioters’ motivation. Evidence of an offender’s mindset is not needed to prove the crime of violent disorder, nor other common charges against rioters such as assault and criminal damage.

Also being sentenced alongside Vint was 21-year-old Charlie Bullock, who was seen launching rocks towards police with his face covered by a balaclava during the Middlesbrough riot. He fought the police who tried to arrest him, and when eventually detained told them: “I couldn’t give a fuck.” He was jailed for 18 months, with the sentence having been reduced because of his young age and evidence that his behaviour may have been affected by a failure to take ADHD medication.

Like Vint, he had refused to answer any questions in his police interview and pleaded guilty to violent disorder without giving evidence in court, but was also found not to have any racial or ideological motivation.

When the time came to sentence a third rioter, who had thrown bricks at police in Darlington on Monday 5 August, the issue could not be so easily resolved.

Cole Stewart, 18, admitted launching the missiles at a line of officers keeping protesters away from a mosque, but claimed a police van was his target and that he held no racist or far-right views. “He came across the protest, having consumed alcohol, and got involved because everybody else was doing it,” said defence barrister Gary Wood. But prosecutors told the court the offence was a “racially motivated attack” and that the teenager’s sentence should be increased accordingly. Judge Laird said a “trial of issue” would be held if agreement could not be reached.

Two other rioters due to be sentenced last Friday had their cases delayed, including a man who was driven from HMP Darlington to Newcastle, instead of Middlesbrough, “in error” and another inmate who refused to leave his prison cell.

Keir Starmer has promised “swift justice” for those who engage in disorder, having overseen the controversial use of 24-hour courts and ramped-up sentences for more than 2,000 adults and children convicted over the 2011 riots as director of public prosecutions.

Legal experts are urging the current government to learn the lessons of that response, and not to repeat the Conservatives’ failure to fully investigate the drivers of that disorder.

Tim Newburn, a criminology professor at the London School of Economics, said that “procedural speed” and punishment had been prioritised over a deeper assessment of how and why the 2011 riots spread.

“The danger in all of these cases is that we reach for a simplistic explanation and that comes to dominate,” he added. “There is the potential that what’s beginning to be revealed in the court is more complex than the political or general narrative. A failure to investigate is to fail to take the opportunity to mitigate future problems.”

Dr Hannah Quirk, a reader in criminal law at King’s College London, said that history has shown that “people just like rioting … some have really nasty motives and some are just vulnerable and get caught up in it”.

She said that the current disorder was much smaller in scope than 2011, but had been similarly “localised” and exacerbated by allegations of racially biased policing.

Thom Brooks, professor of law and government at Durham University, said that the “extraordinary” speed of sentencing was being enabled by a wave of guilty pleas, and may slow when more complex cases reach the courts. “There has been huge effort to get cases in court right away for the obvious reason of deterring people,” he added. “Police and prosecutors also seem to be conducting a social media campaign seeing people named and shamed.”

Minutes after Vint and Bullock were jailed on Friday, Cleveland Police published their mugshots alongside news of their sentences on Facebook. The posts were met by a chorus of jokes, celebratory comments and applause emojis. Bullock’s mother was the only show of support at Teesside Crown Court, holding her head in her hands as his sentence was passed before trying to speak to the teenager as he was taken down to the cells.

As she was helped out of the courtroom by a friend, staff were already preparing for Monday, when a new group of rioters will stream into the dock to hear their fate.