The Real Reason Henry Doesn't Use Contractions On Longmire
While certain key story elements of "Longmire" cover well-trodden territory, their combination sets the series apart from its competition. "Longmire" is both a Western and a cop show, chronicling various criminal investigations by Walt Longmire (Robert Taylor), the sheriff of a fictional region of Wyoming called Absaroka County. His coworkers at the Absaroka County Sheriff's Department can be counted on one hand, so Longmire generally works either largely on his own or with the assistance of some allies from outside the station. Longmire's solitary soul and the series' remote Wyoming setting lend the show its Western flair.
One of Longmire's frequent allies is Henry Standing Bear (Lou Diamond Phillips), a member of the Cheyenne tribe. Henry and Longmire grew up with one another and remain friends into their adulthood. In real life, the Northern Cheyenne Nation exists within the boundaries of the state of Wyoming, and Absaroka County is located nearby within the world of "Longmire." Sometimes, then, Longmire requires Henry's Cheyenne expertise when investigating crimes involving members of the Cheyenne reservation.
One characteristic Henry exhibits throughout "Longmire" is the absence of contractions when speaking — rather than saying "don't," for example, Henry will say "do not" in full. As it turns out, the primary explanation for this quirk lies in the source material for the "Longmire" TV series.
Henry's speech patterns are modeled after his dialog in the Longmire books
In a post to the official "Longmire" subreddit, user apietenpol directly asked why Henry essentially never uses contractions. The most-upvoted comment, by user theTVifollow, replied that it wasn't solely a creative decision by the show's producers or Lou Diamond Phillips, but rather a holdover from the books on which the "Longmire" TV show is based. Author Craig Johnson's website credits him with 17 "Longmire" novels in total, so the TV series has ample material from which to pull. That includes, as explained by theTVifollow, Henry's lack of contractions when speaking.
While this does explain Henry's signature speech pattern in the TV show, there might be a further reason Johnson decided to write Henry's dialog in such a manner. User BobT21, in another reply to the same Reddit thread, stated as anecdotal evidence that a number of Native Americans on a nearby reservation speak in the same manner as Henry. This suggests that Johnson, then, may have modeled Henry's speech patterns on those of a real-life person or persons.
Henry's aversion to contractions, then, is the result of a confluence of factors: Johnson's decision to write the character in such a way, potentially based on a real speech pattern he has observed, as well as the decisions by both the series' screenwriters and Lou Diamond Philips to retain that manner of speaking when bringing the character to life onscreen.