Who is "local copper inspector"?

Question

Jane Marple was an elderly spinster and amateur detective in the village of St. Mary Mead. An Agatha Christie creation, she appeared in 12 novels, starting with Murder in The Vicarage. Although Margaret Rutherford made her famous on the cinema screen during the 1950s and 60s, it is Joan Hickson’s portrayal of her in the classic 1980s BBC series that is closest to the books.

Though she often seemed to be nothing more than a gossipy old woman, Miss Marple was quicker to get information out of suspects than local copper inspector Slack, and her willingness to put herself in dangerous situations meant that she always caught the criminal.

Answer 1

You are not parsing that correctly. It's (local (copper))(inspector Slack).

Copper is a slang term for a police officer.

He is local in that he works in the area.

Inspector is a rank of police officer.

His name is Slack.

He is a policeman in the local area, with the rank of inspector, and his name is Slack.

It would be clearer if it were punctuated "local copper, inspector Slack", but that is awkward in the middle of a setence. Also, many style guides would suggest capitalising the rank as it is being used as a personal title. It's much easier to understand as:

Miss Marple was quicker to get information out of suspects than local copper Inspector Slack, and her willingness..."