The job of the police is to catch those suspected of breaking the law. The job of the Crown Prosecution Service is to decide if those suspected offenders should be charged with an offence and prosecuted. In order to come to that conclusion the CPS applies certain criteria and if various hurdles are met and overcome and non judicial disposals are excluded the suspect is brought to court. Within those processes the CPS must of course consider the evidence collected by police both tangible and available from witnesses. Often that evidence will not be sufficient for CPS to meet its minimum thresholds and the matter will be dropped. It is relatively unusual for the CPS to prosecute when police advice indicates that a charge should not be brought.
Such a scenario appears to have taken place judging by a report recently from Havordwest Magistrates` Court where both a police and civilian expert witness agreed that a motorist driving in a presumably normal manner was not at fault when his vehicle struck a pedestrian at night.The charge of driving without due care and attention could not be proved beyond reasonable doubt.
It seems odd that CPS being aware of the police evidence decided to prosecute. I wrote last month of CPS inefficiencies in London. It seems that the problem also exists over Offa`s Dyke.