Jurors failed to reach a verdict on Wednesday on whether a student who suffered a brain injury at a university fees demonstration was guilty of violent disorder.
Alfie Meadows, 21, was accused along with four others, in connection with the demonstration in December 2010 when a minority of participants in a 10,000-strong protest clashed with police in Whitehall, central London.
After more than two days of deliberations, a jury at Kingston crown court in London failed to agree and Meadows, of Brixton, south London, was told he may face a retrial.
Prosecutor James Lofthouse told the court the crown would consider the next step: "It is very likely we will seek a retrial but we want to consider our position."
Earlier, Judge Paul Dodgson told the jury he would accept a majority verdict, but the panel of seven men and five women were unable to agree.
Judge Dodgson said: "Individual jurors can only speak for themselves on what they believe to be reasonable. You are here as individuals to say 'this is what I think is reasonable in the circumstances'.
If the consequence of that is a disagreement then so be it. That is how the jury system sometimes ends up, that 12 jurors sometimes reluctantly end up saying we can't agree."
Meadows was a second-year student at Middlesex University at the time of the demonstration and said he was hit with a police truncheon as he attempted to leave the area where protesters were being kettled.
He underwent emergency surgery for his injuries and the Independent Police Complaints Commission mounted an inquiry that was subsequently suspended because of the criminal proceedings.
Meadows's co-defendants Colin Goff, 24, Vishnu Wood, 23, and Jack Locke, 18, were cleared of violent disorder. Locke was found guilty of one charge of arson with a majority verdict of 10 to two. He will be sentenced on May 18. Zac King, 21, may also face a retrial after jurors failed to agree a verdict in his case.During the trial jurors were told the demonstration was one of four concerned with the proposed increase in university tuition fees at the end of 2010.
Lofthouse said that it was evident from repeated film clips taken from various angles on the day that Meadows was prominent in the repeated thrusting of barriers towards the police line on Whitehall.
But Michael Mansfield QC, who defended Meadows criticised police tactics of kettling saying they had been "totally counterproductive".
"They had to wait hour after hour. If you put a ring around a number of people, whatever their intention, they're going to get anxious ... They feel trapped, imprisoned ? anxiety, irritation, frustration, anger, hostility. Do you see that escalation?"
Mansfield added that some of the reports recalling the level of violence used against police were a "gross exaggeration of what was going on."
Meadows's supporters, who staged a demonstration outside the court, claimed the trial was an attempt to silence legitimate protest by pursuing the victim of an assault rather than investigating