 When they were finally available, Carter and Spotnitz made some revisions to the script, including "upp[ing] the attitude on Esther's character" and tweaking the way Mulder and Scully react to her.According to Spotnitz, "Kill Switch" was the most expensive episode that the show produced during its original run in Vancouver, and it took a total of 22 days to film.The episode's bridge scenes were filmed at the Westham Island Bridge, which spans Canoe Pass, British Columbia.