It is important to note that if you have an understanding of why such procedures were put into place, it will give one a greater respect for the rights of the accused person and the way evidence is collected. Most police officer are aware of what to and what not to do in the collection and presentation of prosecution evidence, but do not have any idea of the leverages that is awarded to the collection and presentation of defense evidence.
You have got to remember that the principles and restriction as to what a police officer can and cannot do is bases on the principles that it is better for forty guilty people to go free that for one innocent man to be unfairly convicted. You see our founding legal father had experience where the police officer had forgotten the core values and responsibilities of their office. For them Justice took a back seat, and a conviction at all cost became important, hence many innocence people were convicted by over ambitious police officers. In this era police were manipulating evidence and taking advantage of the ignorance of the suspected/accuse person; which also includes collecting evidence unlawfully etc. all in an effort to secure a conviction. Hence the birth of the rules of evidence, the judges rules etc.
It is expected that when police follow these guidelines that are outlined in the Judges Rules and PACE, they ensure that the police do not infringed on the rights of the accuse person. I will suggest that we all abreast our self not only with what is expected, but why these were implemented.
It is also important to note, that the burden of proof lies with the prosecution and the prosecution has an obligation to prove beyond a reasonable doubt that the accuse person commit the offence that he was accused of committing. If there is a shadow of a doubt that, then that accuse person must be found not guilty. Although the prosecution are limited as to what they can do, the manner in which evidence are collected and presented, the defense has the right to do all in its power to prove their innocence. This includes the manner in which they collect and present evidence. If that evidence can aid any court in proving the defendant is innocence of the allegation, then that evidence will be admissible.
This is because that the court is interested in the truth, and it is in the truth you can and will find justice, thus ensuring that an innocence person is not convicted and suffer the consequence of an offence or crime he did not commit. Remember it is favorable for twenty guilty men to go free than for one innocent man to be convicted.
A higher standard is expected from the prosecution. You see the court is only interested in the truth, the whole truth and nothing but the truth.
It is so easy for an over zealous officer (who have personalize the offense or is under presure form a senior officer to gain a conviction in a matter or to bring an end to the investigation) to violate the rights of an accuse person during the process of the investigation. If such violation is brought to the courts attention or the unlawful collection of evidence is discovered, such events may render that evidence inadmissible (unusable) and if the violation of an accused person rights is also discovered, nine out of ten times such will cause the case to be dismissed on a technicality.
It is important that you understanding your responsibility and learn why you are expected to follow the procedure you are required to follow, and in the process preserved the rights of others.