"...a short piece by Mr. Benchley in which he wrote case profiles of suspected criminals in a pseudo-sociological voice. He ended one of his assessments of a degenerate criminal with the notation, 'Can whistle.'"
Can anyone assist?
Here's all I was able to find for him:
The essay “First—Catch Your Criminal” is along the lines you describe, but with no short clinical note about whistling. It can be found in No Poems, Or Around the World Backwards and Sideways (1932), beginning on page 54, and in the Benchley Round-up (1954), beginning on page 183.
There also an essay “Psychical Tic,” found in After 1903--What (1938), beginning on page 33. However I do not have a copy of that book handy to check it for you.
Anyone have an more ideas what work the inquirer may have in mind? Send your answers to firstname.lastname@example.org.