There was a rumor that in the Rittenhouse case, one of the other folks involved had a much much larger actual criminal history then the one they released, but that a lot of the history was hidden in various ways?
This was supposedly misinformation but the details were pretty specific, and they seemed to indicate that there might be a method to basically hide past convictions so a full picture would not be available.
Has anyone heard of something called "Expungement"?
Google got me to these guys: https://www.record-clear.com/
They claim even felonies can be removed, even if there are probation violations etc.
As an aside, there's a ~2hr video floating around the internet of bodycam footage from arm guy's DUI arrest between the shooting and the trail. They dropped it, presumably because an active DUI case makes for a crappy prosecution witness. Police officers don't even get treatment that good. If they get as far as being cited (vs a free ride home, which is what they often get) the prosecution typically makes them plead down and spend thousands doing so rather than just dropping it.
That said, the DUI in question is an example of a lot of things that are wrong with policing (the cops in the video are professional and civil the whole time) and I think it's worth watching just for that.
It becomes a different matter for people who are charged with crimes and otherwise in court, as courts have rules about what criminal history can or cannot be introduced in the court. There's a general principle that a jury shouldn't know about a person's unrelated previous convictions, since it will bias them towards the person being a criminal despite not actually being evidence relevant to the case in question. But I think there are plenty of exceptions, i.e. if the person has been convicted for pretty much the same crime before it can usually be introduced by the prosecution as circumstantial evidence that they apparently have the skills/means/motivation to commit such a crime. But you can't just tell the jury that they have a rap sheet a mile long. I'm not a lawyer and only know so much about this but I believe that usually pretty much the same rules apply to witnesses. You can bring up that a witness has a criminal record if it's somehow directly relevant to their testimony (i.e. they have lied to a court in the past) but you can't just tell the jury that they have a criminal record to try to ruin their reputation. Although it usually fails in practice, the justice system is at least theoretically built around the principle that people can and do change, and so prior criminality shouldn't be held against them if it isn't somehow contributory to the current situation.
Sometimes evidence is not allowed because it is considered prejudicial.
The purpose of a criminal trial is to determine guilt on a specific crime rather than character. That excluded evidence is sometimes allowed at sentencing.
There was controversy in the Rittenhouse case about his prior comments and actions not being allowed into evidence.
https://www.jsonline.com/story/news/crime/2021/09/17/kenosha...