But the Internet's memory means that something being public at time t1 means it will also be public at all times after t1.
You can do something very simple like having a system that just lists if a person is - at that moment - in government custody. After release, there need not be an open record since the need to show if that person is currently in custody is over.
As an aside, the past few months have proven that the US government very much does not respect that reasoning. There are countless stories of people being taken and driven around for hours and questioned with no public paper trail at all.
Democrats love it too.
They call em Jump Outs. Historically the so called constitution has been worth less than craft paper. From FDRs executive order 9066 to today, you have no rights.
Is the position that everyone who experienced that coverage, wrote about it in any forum, or attended, must wipe all trace of it clean, for “reasons”? The defendant has sole ownership of public facts? Really!? Would the ends of justice have been better served by sealed records and a closed courtroom? Would have been a very different event.
Courts are accustomed to balancing interests, but since the public usually is not a direct participant they get short shrift. Judges may find it inconvenient to be scrutinized, but that’s the ultimate and only true source of their legitimacy in a democratic system.
To be this brings in another question when the discussion should be focused on to what extent general records should be open.
Now for a serious answer, what happens in practice in Europe is not secret trials, because trials are very much public. Since there is only so many billionaries, their nephews, actual mafiosi and people with political exposure prosecution, the journalists would monitor them closely, but will not be there on a hearing about your co-workers (alleged) wife-beating activities.
It's all reported, surname redacted (or not, it depends), but we all know who this is about anyways. "Court records says that a head of department at a government institution REDACTED1 was detained Monday, according to the public information, the arrests happened at the Fiscal service and the position of the department head is occupied by Evhen Sraka".
What matters when this is happens is not the exact PII of the person anyways. I don't care which exact nephew of which billionarie managed to bribe the cops in the end, but the fact that it happened or not.
Rank and file cops aren't that interesting by the way, unless it's a systemic issue, because the violence threshold is tuned down anyway -- nobody does a routine traffic stop geared for occupational army activities.
Like everything, privacy is not an absolute right and is balanced against all other rights and what you describe fits the definition of a legitimate public interest, which reduces the privacy of certain people (due to their position) by default and can be applied ad-hoc as well.