noun
arrest on a separate charge
A legal term for arresting a suspect for a minor or unrelated offense when the real suspicion is for a more serious crime, often used as an investigative tactic.
警察は別件逮捕で容疑者を拘束した。
The police detained the suspect by arresting him on a separate charge.
Compound of 別件 (separate matter) and 逮捕 (arrest).