On the one hand, I support such laws because it forces the police to comply with all legal norms when investigating criminal cases. On the other hand, it seems that compliance with all written norms is not always possible during the investigation. I was accused of a criminal offense (it wasn't murder, but it was also very unpleasant) based on the evidence illegally obtained by the police.
I'd disagree on the implementation, evidence should stand alone from the police, the police actions do not alter whether the perpetrator is guilty or not, they not alter whether the evidence is fact or not.
If the police take incorrect actions that is a separate issue and they should be disciplined or prosecuted appropriately.
All evidence should be available to the prosecution and defence and it is up to the court to decide whether the evidence is admissible purely on the content of the the evidence not how it was obtained. We have had cases where perpetrators or others have manipulated evidence into being inadmissible, that should never be the case.
