Did the switchblade in Se7en violate the Chekhov's gun principle?

On re-watching Se7en I couldn't help but question what purpose Somerset's switchblade had. We see Somerset practice with it and it was also shown a couple more times on screen, and hence make it feel like an important item. But there doesn't seem to be made anything out of it later. It seemed like it failed the Chekhov's gun principle.

For those of you who are not familiar with Chekhov's gun, it is a dramatic principle that states that every element in a story must be necessary, and irrelevant elements should be removed.

Now I do understand that this isn't a hard rule and that one of the alternative endings had Somerset use it to disarm Mills, but I wondered if Fincher forgot to remove the earlier blade scenes when changing the ending. Or is there something else that I missed?

I also came across this Reddit post which was interesting enough, but I just wanted to hear more ideas about what the purpose of the switchblade scenes was for the rest of the story.

analysis se7en

Best Answer

It is not completely irrelevant. Somerset used it various times in the film: to cut crime scene tape; remove the backing of a painting; shatter a metronome; and finally, to open the box at the end.

Many other on-screen detectives have used pens, or other objects to handle, or move evidence. Fincher, on the other hand, decided that Somerset had a switchblade, which he is shown using any time he doesn't want to actually touch something. I like to believe that the backstory (that Freeman created for his character) was along the lines of: as a young beat cop, he (Somerset) may have stopped and frisked a street-hood, confiscating his knife. It would have been a relatively minor thing to not turn it in to property and keep it to use as he is shown doing.

The whole switch-blade as a Checkov's gun thing would have been more accurate, if Somerset was shown with it at the beginning and then never again, I suppose, but to me, it is shown enough to be a personal device that Detective Somerset uses, keeping himself at more than an arm's distance away from everything.