"An IC3 male": that's what the police officer called me after he stopped me. IC3 is the code for a black person. I didn't like being called an IC3, but it's better than being called a nigger.

That's what 21-year-old Mauro Demetrio was called as he sat in the back of a police van in August last year. "The problem with you," said PC Alex MacFarlane, who arrested Demetrio during the summer riots, "is that you will always be a nigger … you will always have black skin colour … don't hide behind your colour."

I am a patron of Newham Monitoring project, set up to keep tabs on police behaviour and racist attacks, so I knew about the Demetrio case just after it happened. The moment I heard about it I thought: this is the one! Demetrio had secretly recorded the comments; the officer would be unable to deny what he had said. Here was the incident, I believed, that would finally bring to light the reality of police racism that many of us experience all the time.

This isn't the first time such a recording has been made. In 1991, Malkjit Singh Natt of Forest Gate recorded an officer saying, "go and set fire to yourself", but the case was never brought to trial. In 2005 a savvy teenager (who can't be named) recorded an officer saying he would "smash his Arab face in". That officer was not convicted either. So I had seen it all before. But this was different: this trial was in 2012, and the recording was clear. This had to be the one.

But it wasn't to be. This week MacFarlane was cleared by a judge of criminal racist abuse after two consecutive juries failed to reach a verdict. Prosecutors have decided not to seek a third trial. MacFarlane's defence against the charge was that Demetrio had used the word "nigger" first, in reference to himself. MacFarlane repeated the word, he said, in a misguided attempt to turn Demetrio's life around: "I had formed an impression in my mind that he had low self-esteem," the officer said. "I wanted him to reconsider his lifestyle, to not view his skin colour as the reason behind the problems he had."

Following this logic, if I saw someone in a wheelchair who I thought lacked self-esteem, I could insult them, to make them stronger. Following this logic, we would all feel better if we were insulted, even the police. I am surprised any jury members accepted it. But then for many of us IC3s or IC2s – Asian males – racist language from the police is something we expect. Last year I watched two officers stop and search an Asian man late at night. "Do I look like a terrorist?" the lad asked. "You may not look like one, but you smell like one," was the reply. There was no one recording, and now I wonder if it would have made the blindest bit of difference.

What would get a policeman using such language convicted? Would the jury have to actually witness the offence themselves? Would they have to taste firsthand, as I have done many times, the abuse of power: the kickings, the false arrests, the stop and searches? This was a jury of what are called my "peers" but for them, perhaps, the police appear as upright people, there to help. That may be their cosy reality – but it's a million miles from that of many inner-city youth, who too often experience the police as an occupying force, obstructing their movement and giving them grief.

I was an angry young black man once. Sometimes, when I was desperate, my anger spilt over and I smashed windows of police cars; it made me riot, it made me burn "Babylon", so I understand how many young people feel.

Demetrio tried to do the right thing: he brought his case to court, he was told to have faith, and then he lost. The feeling of injustice he's going through, I have experienced too. In 2003 my cousin Mikey was killed in police custody. My family went to court too, but although the inquest verdict acknowledged that Mikey was killed by the way police restrained him, there was still no justice. I could make a list of others who have died, or been abused by police, but instead I'll quote from my own poem, What Stephen Lawrence Has Taught Us: "Why are we paying for a police force that will not work for us?" More than 10 years on, I am still asking that question.

• This article was amended on 31 October 2012. The original subheading referred to there having been another police acquittal. In fact, the jury was unable to reach a verdict in the case of PC MacFarlane, so he was discharged, not acquitted. This has now been corrected.