The Butler County Courthouse on Saturday was the latest set used by the Netflix drama series “Mindhunter.”

Producer Bill Doyle said the courthouse was selected for filming due to its traditional appearance and the proximity of Butler to the Pittsburgh studio being used.

“We're using everything we can,” he said.

Butler is the northern tip of a shooting zone that was established for logistical reasons. Doyle said keeping the on-location filming within a certain distance from their home base eliminates the need to use additional lodging.

He explained using an actual courtroom, which was courtroom 1, lends authenticity to a scene. But since they cannot move any walls as is possible with a stage, a room must be large enough to be of any use.

The production crew spent the day filming for a few minutes of screen time for an episode of the show, which will debut in 2017.

Doyle said longer scenes need to be filmed on the stage due to the expense of shooting on location.

“It's more cost-effective,” he said.

Filming started in the morning on Main Street, which was closed to traffic for several blocks.

Since the show follows FBI agents profiling serial killers in the late 1970s, vehicles of that vintage were used for that scene. The original entrance to the courthouse, which has not been used by the public since the government center opened in 1991, fronted for the entrance to the Floyd County Courthouse in Georgia.

Despite going through multiple takes, the crew still made it inside the building for interior shots by 10:30 a.m.

Executive producer David Fincher, who directed such films as “Fight Club” and “The Social Network” also is directing this episode.

The series is inspired by the autobiographical book “Mind Hunter: Inside the FBI's Elite Serial Crime Unit.” Co-author John Douglas is a former agent and one of the first criminal profilers.

For the next scene, actor Jonathan Groff playing the lead character Holden Ford, who is based on Douglas, walked up the courthouse steps from the first floor as extras garbed in brown and tan suits with wide lapels descended.

Fincher reshot the scene until he was satisfied it was right. Once that stage was done, the crew wasted no time moving all the cameras into courtroom 1.

The ensuing scene entailed a conversation following a court proceeding.

Groff, who is known for appearing in television shows such as “Glee” and providing his voice to the Disney animated movie “Frozen,” and other actors in the scene went from memory reciting their lines. No teleprompters in sight.

Doyle praised the work of the cast and the director.

He said Fincher is present during all production, even the episodes he does not direct.

“He's the gatekeeper,” Doyle said.

Doyle also has a high-profile resume, working on such films as “Batman v Superman: Dawn of Justice.”

To provide the required lighting effects, the crew shone spotlights into the windows from cranes. A helium-filled fabric covering mitigated the glow emanating from the lights above the courthouse stairwell.

Doyle said such methods even out the lighting, eliminating shadows.

“It's controllable,” he said.

The crew also used its own generator to power all the equipment. Covered wires were strewn across Diamond Street, which also was closed to traffic.

Private security walked the exterior Friday night to ensure nothing outside was disturbed.

The equipment was removed Sunday.

The crew filmed additional scenes along Route 8 in Penn Township two weeks ago. Doyle could not divulge where filming would resume in Allegheny County today.

He said if Netflix orders a second season of “Mindhunter,” production could return to Butler County down the road.