I have an experience where a trooper lied to the court twice and I have evidence to back it up. Nobody cares. I tried a the ACLU (bigger fish to fry), a complaint with the department (they counseled him and made the excuse that they have a lot of new guys at this station), I wrote my state representatives multiple times (no reply, except for one, which was a form letter not even applicable to my scenario), we tried the DA's office (they participated in multiple rights violations), we tried the DoJ for civil rights violations (no updates for about 6 months), we submitted complaints against a magistrate and a judge with the board of conduct (no updates and over 6 months), we submitted complaints against the ADAs who participated in incompetent or misconduct to the Bar (was told they only investigate prosecutors if the court formally determines there was prosecutorial misconduct), talked to an civil rights lawyer (was told it was a violation, but the courts don't care unless large monetary damages were involved), and talked to an investigative journalist (ran a story similar to this but said to keep him posted if I find anything explosive).
There's literally nobody to turn to. Almost every person involved in the system made mistakes or misconduct during the process (cop, 2/3 magistrates - 3rd was arrested for an unrelated matter, the judge, 2 ADAs, etc). I have absolutely zero faith in the system.
Judges generally aren't involved I'm the removal of an officer. That typically happens via IAD, and even then the union tells them to resign so the IAD investigation ends and they can just go to a different department.
My wife an I both witnessed him say he was amending the charge because he made a mistake. He then went into the court and told the magistrate he was amending the charge to "cut us a break". The magistrate then issued a continuance (instead of dismissing if he knew the true reason). The incorrect charge carried pretrial restriction only found under that charge and the trooper knew that the charge was incorrect for about 6 weeks. State law only allows amendments if the rights of the defendant were not violated (there were 2 other rights violated later, and multiple procedural mistakes too). Subjecting someone to pretrial restrictions under a charge that is known to be wrong is unusual punishment and also a violation of the state constitution. So it would require dismissing the case. We found proof supporting this in the trooper's later testimony where he stated that he knew it was incorrect for those 6 weeks, yet held it against us anyways. The IAD investigation found that he did tell us the correct thing and then told the court something wrong 10 minutes later. The report said it was a "misunderstanding", without any details or explanation.
Later he claimed that a picture he introduced in court was in the investigative file "since the beginning", yet it was not furnished to us when we subpoenaed the file. Another IAD investigation found that the picture wasn't placed in the file until a later time. The magistrate did not throw out the picture because he thought we had access the whole time and we didn't have access to that IAD finding until after the trial (not sure if I trust this or they were covering). Furthermore, the picture was exculpatory evidence under the incorrect charge and should have been furnished to us regardless of the subpoena. So much for Brady...
He made 2-3 other factually incorrect statements that I did not have hard evidence of (just our word against his). These included things like changing his story in a contradictory way. We did have a recording of his testimony and a phone call with him (both consistent with law).
The complaint process also treated us adversarially, which is a violation of feral policy (hence complaint to DoJ). The state police claim they can knowingly hold incorrect charges against people.
This has never stoped them from lying, since they already know who will be believed.
Are you talking only about evidence literally gathered with a gun pointed to your head? If, so, well, my comment wasn't that literal. As a rule, if you have any chance of becoming a suspect, the police here will refuse to interrogate you without your lawyer around, because listening to you can jeopardize their work.
There are two classes of damages police can enact on you in the US, both of which makes interacting with them in any capacity dangerous.
The first class is that they can completely ruin or end your life. This includes anything from killing you, leaving you with lifelong injuries or stress disorders, felony charges, etc. Anything that permanently scars your enjoyment of life.
The second class is non permanent, but extremely inconvenient damages. These are very common, take little effort or thought on their part, and ranges from impounding a car, charging you with a misdemeanor, harassing you, taking large sums of cash from your person, disturbing your house or belongings, trespassing you, holding important belongings or documents as evidence, etc.
Either of these classes of damages can be the result of an interaction with police, stemming from saying the "wrong thing", "acting nervous", "acting suspicious", being in the vicinity of a possible crime, being accused of witnessing an event, being too close while they are conducting police business, "making them feel uncomfortable or unsafe", being the victim of a crime, etc.
Each time you speak to police, you risk a chain of events occurring that result in one of these two classes of damages. It's just not worth it. They aren't worth talking to, given some of the possible outcomes.
Basically if you don't interact with police at all you can't have bad (or good) interactions. Since there are lots of things (race, wealth as indicated by clothing or vehicle, someone having a bad day, ticket/arrest quotas, etc) that can make interactions worse and few that can make them better it's often easier to just avoid contact.
Personal example: I'm doing laundry at a laundromat following the tragic death of a washing machine not long ago. On a recent Sunday night the attendant appears to have quit sometime in the afternoon or early evening (note on the counter "back in 2 hours" but clearly gone much longer than that). I cleaned up the place a bit while my stuff was in the dryer, but since I was the last person there and it was after their last load (and no answer on any of the numbers on the call list behind the counter), I called the local police to see if they could have patrols keep an eye open overnight. I felt fine doing that as a late middle age white guy in whitebread suburbia, but if I was a 20something minority? I suspect the wisest move would be to simply finish my laundry and leave just like I would any other visit to the business.