Each creature and monster in the Witness Articles was created with practical effects and costuming. While effects were added to the shadow people in post-production to enhance their phantom like presence, actors still wore costumes on set.
All episodes were filmed within close proximity to Sydney, NSW Australia. Many of the more elaborate set pieces such as the dugout in The Hound of Hell and the catacombs in Where the Jackal Sleeps were built in a studio.
As a homage to classic horror and film-making, Easter eggs referring to famous horror movies and classic cinema is hidden throughout each episode of The Witness Articles. An example of this is Greg Poppleton's character who appears in the episode A Den for Sheep Pt. 2. The name of Father Damien Merrin is an amalgamation of Max von Sydow's character in The Exorcist and the character of Damien from The Omen.
Actor Bilal Dannaoui seemingly disappeared before the opening scene of Wolf of the Woods could be filmed. Director Ryan Stubbs needed to use a stand in and film the two-hander scene without showing either of the actors faces as Tristan McKinnon's face was not to be revealed until A Den for Sheep Pt. 1.
Oscar Fleming was originally set to reprise the role of Brad Barnes in A Den for Sheep Pt. 1 in a scene that takes place in a prison. However due to scheduling conflicts the scene needed a major rewrite and Mark Nichols' character, Julian Porter, was created to replace the role of Brad Barnes and the location was switched to an Asylum.