No, it’s not a perversion. The criminal justice system is built on a series of steps, and to pass each step, the state must meet an increased burden of proof/review. The burden on the prosecutor is higher than the burden on the police, for good reason.
The police themselves have to meet a series of increasing proof. They can’t just stop anyone walking down the street. They have to have, at the very least, a reasonable suspicion that something has happened, and that a person may be a witness. That is a very low standard, appropriate for the very beginning stages of an investigation. But, that type of suspicion only justifies a very short detention, to start the investigation. Reasonable suspicion doesn’t justify the laying of a criminal charge.
To lay a charge, the police have to meet a much higher standard than reasonable suspicion: that is what probable cause means. They have to have probable cause to believe an offence has been committed by a particular individual, based on their investigation and their understanding of the law.
But once charges are laid, it goes to the prosecutor, and the prosecutors have a different, higher, standard. Prosecutors are not the lawyers for the police, and do not proceed to trial simply because the police have laid a charge. They are independent officials in the criminal trial process, and they must conduct their own assessment of the case, using a higher standard than the probable cause required for a charge to be laid.
In my jurisdiction in Canada, it’s usually stated as the prosecutor must be satisfied that “there is a reasonable likelihood of conviction.”
(See Federal Prosecuctions Policy: “Proceeding with Charges.”) That assessment is based on a more detailed review of the law than is possible for a police officer, and also on the prosecutor’s professional review of the evidence available, in light of the trial process. The witness statements and other evidence may indeed support probable cause, which is the standard the police must meet. But, the prosecutor may conclude that there are difficulties with the case as presented, which make a conviction unlikely.
[ul][li] If there are serious conflicts in the witness statements, for instance, which is certainly the case in the Ferguson case, that may lead the prosecutor to conclude that a conviction is unlikely.[/li][li]Or, it may be that some of the evidence is inadmissible, due to constitutional or statutory restrictions.[/li][li]There may be serious credibilty problems with some of the witnesses.[/li][li]Witnesses may no longer be available to testify, due to illness, death, or having moved.[/li][/ul]
If a prosecutor concludes that there is no reasonable likelihood of a conviction, they don’t just have discretion to stay the charges: they have a duty to stay the charge. If the prosecutors, based on their professional skills and experience, conclude that there is no reasonable likelihood of conviction, then they must stay the charges. The state at this stage must meet a higher standard than probable cause, and the prosecutor has a duty to ensure that higher standard is met. If not, the charges must be stayed.
And note that the standard continues to increase as the matter proceeds. At the preliminary inquiry stage, held before a judge, the prosecutor must lead all the evidence and have the judge make an independent assessment whether there is sufficient cause, in the judge’s view, for the matter to go to trial. The judge makes that assessment based on submissions from both the prosecutor and the defence.
Then, finally, at trial itself, the prosecutor must prove the case beyond a reasonable doubt. That is a higher standard still, higher than both “probable cause” and “reasonable likelihood of conviction.”
This series of increasing burdens on the state is intentional and a crucial part of the criminal justice system. It is designed to protect the accused from the state. At each step, the state’s onus increases, to weed out the cases that do not have merit and to ensure that only the guilty are convicted.
As others have commented, trials are not fact-finding processes. They are not to be used to “clear the air” or to demonstrate that the state has properly investigated a case. Their purpose is for the state to prove that an accused has committed a crime and should be convicted, possibly incarcerated.
If at any stage in the process, the state cannot meet the increasing burden, then it must stop the investigation, the charges, or the trial. Anything less would be a perversion of justice.