A man who spent three years and £100,000 trying to bring his attacker to justice is preparing for a new trial after the Director of Public Prosecutions promised to reinvestigate the case.

Coventry businessman Joe Richards – who has no legal training – discovered an exception to the principle that no one may be tried twice for the same incident, which may lead to his attacker facing more serious charges than those for which he was originally convicted.

Mr Richards suffered multiple skull fractures, a brain haemorrhage, spent two weeks on a life support machine and almost died after being hit on the head by a stranger with a bottle in what he maintains was an unprovoked attack.

Three years on he continues to suffer brain damage, which deprives him of his sense of taste and smell and leaves him prone to bouts of anxiety.

After the assault his attacker pleaded guilty to wounding and was given a £500 fine and ordered to carry out 200 hours’ community service.

Despite Mr Richards’ claims that he was hit in the back of the head in an unprovoked attack, his assailant was sentenced on the basis that he was provoked and that he hit Mr Richards from the front.

But at no stage was this assertion tested in court because of the defendant’s guilty plea – denying Mr Richards the justice he sought.

Since that day, Mr Richards has been researching the law and has now identified the Exception to the Elrington Principle, whereby someone may be tried for an aggravated version of the same offence for which they were convicted.

He has the support of leading barrister Hugh Tomlinson QC who has written an opinion which has been sent to the Director of Public Prosecutions (DPP).

In response, the DPP said in a letter to Mr Richards that as a result of his submissions, a number of inquiries would be made.

Now Mr Richards is awaiting the results of these inquiries.

He said: “I believe I have done enough to get this case reopened. If it is, it will go some way to restoring my faith in the justice system.”

In order for the Exception to the Elrington Principle to apply, there must be compelling new evidence against the defendant and it must be in the interests of justice.

Mr Richards has evidence from a consultant neurologist and a consultant neuro-radiologist that states that injuries were caused to the back of his head, as well as witness accounts consistent with this.

Mr Tomlinson says that this new evidence, coupled with the fact that it is clearly in the public interest for perpetrators of violent offences to receive appropriate sentences, means that the exception should apply and Mr Richards’ attacker should be retried for a more serious offence.

There are two possible courses of action: a new prosecution for the assault, or charging Mr Richards’ attacker with perverting the course of justice, since he argued in court that he was provoked.

Mr Richards, who built up a chain of 12 fruit and vegetable shops after starting out with just a market stall, said: “My attacker has given me a life sentence – I have to live with what he did every day.”