Yesterday outside the High Court in Livingston, Gordon Johnstone cut an anguished figure as he tried to make sense of the senseless.

His daughter Annalise had been murdered. His son Jordan walked free from court as the jury found the murder charge against him 'not proven'. Earlier, a judge had ruled there was insufficient evidence against another co-accused.

Gordon Johnstone cannot make sense of the not proven verdict. He is not alone. Over the decades every time a jury reach such a verdict there are calls for it to be scrapped. Questions are inevitably raised in parliament.

Politicians pledge to review it but inevitably a two-day story goes away until the next time a jury reaches the same conclusion.

So what are juries actually told before they retire to consider a verdict? A judge will explain that there are three possible verdicts: guilty, not guilty and not proven. They are also told that not guilty and not proven essentially mean the same when it comes to the charges against an accused; they are both verdicts of acquittal.

Very little, if any, direction is given to jurors to cite the circumstances in which they may want to opt for a verdict of not proven as opposed to not guilty.

Arguably the more important explanation a judge gives to a jury is defining what 'beyond reasonable doubt' means. That is the evidential standard of proof that the Crown must establish in order to secure a conviction.

This charge makes it clear that if a juror is in anyway unsure about any of the material evidence as it relates to an accused then they must acquit as they will have a reasonable doubt. They then have to choose between the two verdicts of acquittal - not guilty or not proven.

Some who argue for the abolition of not proven believe that a jury may well opt to find an accused guilty if the 'cop out' verdict of not proven is not available. That view is erroneous. What sinks a Crown case against an accused is not the range of verdicts available to the jury, rather the very high standard of proof placed on the prosecutor in a criminal trial.

The only effect of abolishing not proven is that juries will return a verdict of not guilty since that conclusion is driven by a reasonable doubt over the evidence.

So why do jurors opt for not proven? It's impossible to say for they are not interviewed at the end of trials and what is said in the jury room remains in the jury room. It is the legal equivalent of the seal of the confessional.

There is probably something in the view that in returning a verdict of not proven jurors are essentially saying, we think the evidence against an accused is strong but doesn't quite reach the standard of beyond reasonable doubt.

I have always had a problem with the available verdicts but curiously my concern is with guilty and not guilty. Guilt beyond a reasonable doubt seems to me to suggest there is little room for getting it wrong.

It appears to be final and beyond reproach and yet there have been hundreds of convictions set aside over the years where the appeal court has decided that a conviction is not safe.

Someone tarred as guilty has had that guilt expunged on appeal but only after their reputation has been tarnished beyond repair.

I think the only two verdicts which make sense are that of proven and not proven. The essence of a jury trial is to establish if there is evidence, beyond reasonable doubt to allow a jury to convict. That is a different matter from the rather certain issue of guilt. The best the system can do is to prove a case or not prove it.

Perhaps the debate that is needed is not about scrapping the not proven verdict but scrapping the verdicts of guilty and not guilty.