A student who gathered video evidence of himself being harassed and abused on a pair of specially adapted sunglasses has been allowed to carry out a private prosecution of his tormentor.

The highly unusual case, in which the Crown Prosecution Service declined to take over or halt the proceedings, may point the way – in the era of technology such as Google Glasses – to a future of do-it-yourself justice.

Haresh Mehta, 20, who lives in Southampton, complained repeatedly to the police about insults and intimidation he was enduring. Officers were called out several times but on each occasion, he maintains, the incident resulted in counter-allegations from his tormentor and no formal action being taken.

Determined that his persecutor should answer before the courts for the campaign of vilification, Mehta, who is studying IT security at university, purchased a pair of surveillance sunglasses which contain a video recorder hidden in the frame.

“It was like having a camera between your eyes,” he explained.

“There had been between five and 10 incidents. Whenever we called the police … counter-allegations [were made]. I thought I should have independent evidence. The first time I went out with the sunglasses on, [he] swore at me.”

The man was alleged to have told Mehta: “Get out of the car, you little cunt.”

The charge, brought under section 5 of the Public Order Act 1986, said that the defendant’s conduct involved “threatening, abusive and insulting words or behaviour … within the hearing or sight of the informant [Mehta] which caused him harassment, alarm or distress”.

Mehta’s tormentor, who pleaded guilty when the case came up at the city’s magistrates court, cannot be named for legal reasons.

He was given the option of paying a £500 fine or serving one day in custody; he chose the day’s custody as punishment.

One of the unusual aspects of the case is that the CPS considered the video evidence, concluding there was a realistic prospect of conviction and that it was in the public interest for the case to go ahead. Nonetheless, the public prosecutor declined to intervene, observing that both parties were represented by lawyers.

Lawyers for the defendant had written to the CPS asking it to take over the case.

The CPS letter sent out earlier this week informed Mehta’s lawyers that the video sequence had been scrutinised and showed sufficient evidence of an offence.

“I have considered the views of the alleged victim, Mr Mehta,” the letter continued.

“He has brought a private prosecution in this matter and so I am satisfied that this incident has clearly had an adverse impact on him.

“Taking all these factors into account, I have concluded it is in the public interest for this prosecution to proceed … the facts of this case are narrow and straightforward. There are no complex issues that require the intervention of an independent prosecutor … I have therefore decided not to intervene in this matter.”

In the event the defendant pleaded guilty so the way in which the video evidence was obtained and its veracity was never an issue.

The case has emerged as police forces across Britain are gradually being fitted with body cameras and courts are being provided with video screens to speed up the justice process.

The widespread availability of digital video technology means many more cases involving conclusive video evidence of crimes could be used in court by individuals seeking justice as well as by police officers.

Gareth Jones, a solicitor with the London law firm Rustem Guardian, gave Mehta advice, on a pro bono basis, about pursuing the case.

“This is very rare. This is the first time we have done a case like this,” he said. “[The family] felt very strongly they did not want to suffer at the hands of [this bully].

“If it was the CPS themselves doing it, it might have cost them a lot of time on a not very serious case. But in the overall scheme of things, you can’t have people behaving like this. The evidence was all on camera.”

A CPS spokesperson said: “We decided that there was no need for the CPS to take over this prosecution and therefore the private prosecution should be left to continue.

“This was regarded as being a straightforward case in which both parties were legally represented.”