This has been bothering me too, but then I found this:
Supreme Court of Appeal
Director of Public Prosecutions v Mtshweni
Case No. 52/06
If the error is one on which the acquittal of an accused turns then there is a grave irregularity in the proceedings and the court of appeal is bound to order a retrial on the same or amended charges. Question of law reserved answered in favour of the State, and institution of retrial ordered.
[32]
It is clear, therefore, that there is no argument before this court that where a trial court has erred on a question of law, the institution of a new trial will infringe s 35(3)(m). The possibility of double jeopardy does not arise. And, as the State argues, there will be a serious miscarriage of justice should a proper trial not ensue. It is not only an accused whose interests must be protected by the criminal justice system. There must be fairness to the public, represented by the State, as well. There must be fairness to the victims of the crime and their families. In S v Jaipal17 the Constitutional Court said:
The right of an accused to a fair trial requires fairness to the accused as well as fairness to the public as represented by the State. It has to instil confidence in the criminal justice system with the public, including those close to the accused, as well as those distressed by the audacity and horror of crime.
Paras. 28-34 are all well worth reading.
http://www.saflii.org/za/cases/ZASCA/2006/165.html
mrjitty, could you please have a look at this decision and advise.