police beat

Miyuki MiyabeのCrossfireを読んでいます。
The investigation team had quickly interpreted the three cases, or at least the Tayama factory and the Sakurai Liquors cases, as fallout from escalating friction within Asaba's gang. While they didn't go so far as to announce their interpretation at a press conference, they did leak it to individual reporters on the police beat. The mass media took it up under headlines that competed for sensationalist effect: "Violent teens," "Sharp rise in vicious crimes by juveniles," and "Call to revise the Juvenile Protection Act"--all followed by articles that were portraits of cold-blooded criminal teens with no respect for human life.
"police beat" の意味を調べます。まず "beat" を辞書で見ます。
・Macmillan Dictionary: an area that a police officer has responsibility for and must walk around regularly: walk/pound/patrol the beat: The two officers used to walk the beat together.
・Oxford English Dictionary: An area allocated to a police officer to patrol.: a patrolman who strived to make his beat a safe one
Googleで調べるとOxford Dictionary of Journalismに次の説明がありました。
beat: Primarily a US term for the subject matter or geographical area that a reporter might be assigned to cover, as in 'the crime beat' or 'the Washington beat'.
更に、ThoughtCo.のWebサイトに Covering the Cops (https://www.thoughtco.com/covering-the-cops-2073873)と題された記事があり、"police beat" について次の説明がありました。
The police beat can be one of the most challenging and rewarding in journalism. Police reporters get to cover some of the biggest breaking news stories out there, ones that land at the top of the front page, website or newscast.
But it isn't easy. Covering the crime beat is demanding and often stressful, and as a reporter, it takes time, patience and skill to get the cops to trust you enough to give you information.
"reporters on the police beat" は警察担当の記者と解して良さそうです。