R v A [2008] EWCA Crim 1034, [2008] All ER (D) 222 (May)
The scheme for prosecution appeals under s 58 of the Criminal Justice Act 2003 is that proceedings in the court below stand adjourned pending the hearing of the appeal, and the ruling is to have no effect pending the outcome of the appeal.
It follows that where a defendant has been acquitted following a ruling of the judge, the prosecution cannot seek to appeal against that ruling. The prosecutor could have given notice that he intended to appeal the ruling, and if he had, that ruling would then have been of no effect pending appeal. Prosecutors who wish to launch appeals against rulings must give the s 58(8) undertaking in open court at the time of invoking the right of appeal.