"It Is Possible to Cover Up a Crime Too Well"

"The Seventh Man."
By William Byron Mowery (1899-1957).
First appearance: Adventure Magazine, October 30, 1923.
Short short story (5 pages).
Online at Archive.org (HERE).

"There were but two ways of finding out the murderer."

Even in the Great White North, closer to the Arctic Circle than most people will ever dream 
of going, if there's a murder there has to be an investigation. When a fur trapper named Nascaupee Neilson—"the most jovial and likable mixture of French and Scotch on the Koksoak"—is found dead, Bent Avery takes it upon himself to determine which one out 
of dozens of roughneck trappers, prospectors, and fishermen committed the crime.

Through a careful process of elimination, Avery has narrowed his suspect pool down to just seven men, and because the victim was so well-liked he has decided to present his case to the world at large, in this instance everybody at Fort Chimo, knowing full well that when he finally fingers the murderer there's almost certainly going to be a full-scale riot, which is why he keeps his Mannlicher–Schönauer carbine handy:

"First [he tells them], understand I am bossing this affair from beginning to end. I know what some of you have been saying and wanting to do. All your spruce-limb parties couldn't find out for sure who killed Nascaupee Neilson. I've taken the affair into my hands and I'll enforce order—and protect the murderer—with this, if necessary." He tapped the magazine of his rifle. There was a growl of surliness in the crowd.

While everyone else was out running around trying to track the killer down, Avery himself made an important discovery—and a deduction:

"I said there was not one positive clue in the cabin of Nascaupee Neilson. There was a clue, of a sort. It was left behind to cover up the crime, to throw the blame upon an innocent person. That is the sole clue I had to work with."

The clue he's talking about is the murder weapon itself. An odd thing about that clue, though—there's another one so much like it that it's almost impossible to tell them apart . . . almost . . .

Resources:
- Our author, William Byron Mowery, was actively writing from the 1920s all the way into the '50s, mostly outdoor adventure stories; FictionMags describes him thus: "Teacher, naturalist and novelist. Born in Adelphia, Ohio; on faculty at University of Illinois, then became full time writer, with more than 450 published stories, screenwriter." PulpFlakes also has a short article about him (HERE).

The bottom line:
   An ugly knife lay buried
   In the heart of 'Mad' Carew ...
   'Twas the vengeance of the little yellow god.
   — John Milton Hayes