[jcrawfordor]

Most US states have some form of expungement law which allows past criminal records to be cleared. It's mostly intended to help ex-cons with reintegration, because it can be so difficult to get employment (and in many cases voting rights, public services, housing, etc) with a criminal history. Basically criminal records are a major part of the "cycle of criminality" that causes recidivism because former criminals are unable to support themselves by means other than crime (can't get a job, etc), and so expungement policies are expected to have a positive impact on both crime and social welfare. The details all vary from state to state, often there's a limit on how severe of an offense can be expunged, it has to be a certain time in the past, and typically the records are not really "expunged" but removed from public reports---law enforcement and judges can often still see them, as well as federal background checks, and sometimes anyone can ask for a court order to unseal. The expungement itself usually requires a court order, so the court makes a judgment whether or not expungement serves the public interest (i.e. will allow the person to contribute more fully to society). There are a lot of law firms like that that specialize in expungement because there are many people with criminal records and in most cases the process is a pretty straightforward paperwork exercise, so you can make a steady profit stream with a few paralegals preparing form letters.

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.

[rak]

To add to this, a lot of times expungement isn't very useful because there are a ton of private companies that scrape these records (including arrest records) constantly. Some of these companies have business models built around conducting background checks and an unfortunate number of them have business models that rely solely on getting people to pay them to "remove" these records.

[jcrawfordor]

Yes, this is a big issue! Part of the reason why e.g. California and other states have introduced "ban the box" legislation to restrict employers asking about criminal history, when they already have an expungement process, is because of this issue exactly. Most pre-employment background checks are done through vendors like LexisNexis that pull records at the time of the incident and then retain them permanently, so expungement doesn't do anything. The whole private background check and criminal records industry can be surprisingly sketchy, including behavior that looks to reasonable people like extortion, but it's resisted almost any regulation or oversight. Some of this comes from an inherent tension between public records and personal privacy (are the actions of law enforcement a matter of public interest or a matter of personal privacy? the line can be very blurry), but a lot of it is also just because this industry is politically and financially powerful and any action against it tends to look "soft on crime."

[hguant]

The accused's criminal history comes up more in sentencing than it does in actual criminal cases - in the US system you're being tried on the crime before the court, not anything from your past. There are obvious exceptions - someone who is suspected of murdering their spouse who has prior domestic violence charges is one you see a lot - but in general, that comes up during the sentencing, where the judge has a lot of leeway to tailor the sentence to the circumstances.