on CMOS Shop Talk:
I gave Detective MacSwain $200 and a diamond ring worth $1,000 to keep quiet and make it look like suicide. (Dashiell Hammett, Red Harvest, 81)
“That’s nice,” the gray-mustached sleuth on my left said. He didn’t sound sincere. . . . The gray-mustached detective who had sat beside me in the car carried a red ax. (Red Harvest, 106)
Few readers will be puzzled by the capital D in the first example and the small d (and s) in the second. “Detective MacSwain” is treated like a name, a proper noun; “detective” (like “sleuth”) is a common noun. But what form would you choose in the following examples?