There doesn't seem to be an "official" collective noun for detectives. Detectives are people, so the traditional collective nouns would be words appropriate to the context, such as a team, a crew, a shift, a group, or a squad.
There are many suggested collective nouns for detectives, however. Some have been used in published works, while others have just been suggested by different collective noun advocates:
Troupe
Gang
Nonn
Group
Posse
Shoal is a collective noun. It is the collective noun for fish. A shoal of fish.The collective noun is a mint of candies
There is no standard collective noun for a group of reflections. The noun 'reflection' is not a standard collective noun.
No, the noun lumber is not used as a collective noun. The collective noun for lumber is a stack of lumber.
No, the noun farm is not a collective noun.
No it is not a collective noun.
Shoal is a collective noun. It is the collective noun for fish. A shoal of fish.The collective noun is a mint of candies
There is no standard collective noun for a group of reflections. The noun 'reflection' is not a standard collective noun.
No, the noun lumber is not used as a collective noun. The collective noun for lumber is a stack of lumber.
No, the noun farm is not a collective noun.
No it is not a collective noun.
The collective noun is a series of explosions.
No, the noun land is not a collective noun. However, any noun can function is as a collective noun in a suitable context without being a designated collective noun.
No, games is not a collective noun. The collective noun for games is 'a compendium of games'.
The collective noun is an anthology of poetry.
The collective noun for 'wheat' is a sheaf of wheat.The collective noun for 'barley' is a crop of barley.
The collective noun is a drift of icebergs.
No, the noun 'kin' is not a collective noun.