A police officer has less credibility than the defendant. Similarly for prosecutor expert witnesses, police forensics, police crime lab work, etc.
In front of me, super tough, nearly impossible, for a public prosecutor with just police evidence to convict anyone of anything. The prosecutor would be wise never to use any evidence that in any way had anything to do with the police.
Get some other, solid, clearly objective evidence or the defendant goes free.
And for statistical evidence, I know some statistics, at an advanced level, and doubt that there is a single prosecutor in the country who could even once put on statistical evidence that I would find less than just fraudulent. E.g., lie detectors, finger prints, and much more -- garbage. DNA? Not from a crime lab.
As soon as the prosecutor or one of their witnesses mentions prior police record of the defendant, the defendant goes free. Why? Constitutional protection against two convictions, or or even two trials, for the same event. The issue is what the defendant did as charged this time -- whatever they did in the past is just irrelevant. A second trial for an earlier event is unconstitutional and an attempt at what I call fraud and, thus, no more reason to listen to the prosecutor. I call it fraud: On a jury, I get to call fraud anyway I want, and I don't have to explain.
Have the defendant locked up for more than a week without trial? Violates the constitutional guarantee of a speedy trial. Defendant goes free.
Defendant injured while in police custody, whether from the police, other people in the jail, or just a brick falling out of the sky, violation of the constitutional guarantee against cruel and unusual punishment and taking the freedom of a person without due process, and the defendant goes free and wins a civil case against the city, etc.
Can't take a person's freedom, not even for a day, without taking care of them, e.g., having a social worker inform all their family, make sure their house is secure and their kitty cat fed, etc. Fail to do that, and that violates the constitutional guarantee against cruel and unusual punishment and also punishment without due process -- defendant goes free.
There is an easy solution -- put me on the jury.
Then when the defendant goes free and brings a civil case against the prosecutor and police, tough for the former defendant to lose that case. Have the city, whatever, pay them the $5 million or whatever.
Net, in front of me, the police, prosecutors, etc. have to clean up their act, scrub 100% clean, at least as in the Constitution, or the defendants will go free, just as the founding fathers intended.
The police stopped the car because the driver failed to use a turn signal? BS. Likely the police are lying, and in that case the stop was a case of unconstitutional "unreasonable search". That's my view, and on the jury I get to vote that way for any reason or no reason and don't have to explain my reason.
A police officer killed an unarmed person? Deliberate, unprovoked, unexcusable murder. Life or the chair.
The police have tracked mud all over our Constitution, and it's long time since that was way too much.
Defending our Constitution is much of why we want police.