Yesterday's announcement that the Crown are to seek the High Court's permission to try the man suspected of "The World's End Murders" for a second time is a new low point in the recent history of Scots criminal law.

Like all other civilised democratic systems, Scots law has proceeded for centuries on the basis of prosecution being a matter for the Crown, not for he who claims to be wronged. The traditional Scots prosecutor decided whether to proceed on the basis of the public interest, not on the basis of the private desire for vengeance – or "search for justice".

Along with some other questionable developments in the law from the Scottish Parliament, siding with self-proclaimed victims who shout the loudest irrespective of the general public's interest, the consequence is a return to an approach that is a relic of old and barbarous times. Indeed it is pre-Christian, Christ having been scathing about it in his ministry.

But now it seems Scottish MSPs have decided to throw centuries of wisdom into the bin and change aspects of Scots criminal law into a near neighbour of Islamic Sharia law. Not only has the Scottish Parliament altered the hugely important principle that an accused can be tried only once for a crime; it has gone further and made the abolition of double jeopardy retrospective.

That retrospective quality of the 2011 Act is what allows the Crown to make yesterday's application to the Court. So the fact that Angus Sinclair was first tried for these murders before the 2011 Act was law can be got round.

This is not some fancy lawyers's point. It is one of fundamental fairness observed in mature democratic legal systems. How would like to be told that you are to stand trial for wearing a hat – should the Scottish Parliament decide to outlaw hats in 2013? Would be happy to pay extra income tax for 2012/13 if Holyrood decides to retrospectively impose new taxes in 2014?

The great American trial lawyer, Clarence Darrow, rightly observed that the most important legal principles emerge from cases involving less than attractive people and often horrific facts. In Scotland, so far we have been sensible enough to appreciate Darrow's point. Now, as we seem destined to enter some sort of legal second childhood, we seem to be forgetting the principles which used to make Scots law a system to be proud of.

l Alistair Bonnington is a former lecturer in criminal procedure at Glasgow and Strathclyde Universities