.

At the hearing in the absence of the accused, the court ordered pre-trial detention (with respect to the accused)

мера пресечения в виде заключения под стражу - pre-trial detention. "Избирает" ее суд путем вынесения своего order. По поводу "заочности", да, нужен раширительный перевод

The context is a bit long-winded, to me, in English it should sound like this:Preventive detention in-absentia was/has been applied/used against the defendant or the accused.
or
The defendant/accused were/have been placed in preventive detention in the absence of the defendant/accused.
In English it must be short and clear, I don't think we should use imprisonement, arrest or incarceration. Detention means the same thing. Preventive detention is an imprisonment that is putatively justified for non-punitive purposes, most often to prevent further criminal acts.


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Note added at 1 day 17 hrs (2024-04-03 15:41:02 GMT)
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Preventive detention is also used when the release of the accused is felt to be detrimental to the state’s ability to carry out its investigation. In some countries the practice has been attacked as a denial of certain fundamental rights of the accused.