The courthouse used in an establishing shot is clearly something filmed from an earlier era (or it’s a period piece). The cars are too old, and one can barely make out that the fashions as certainly pre-1950s. Submitted by gracep, 8/31/2010. Picture here.

The courtroom (brick style with vintage pictures) setup and the judge (Jamie Forster) are a reuse from prior episodes when they had a country trial. Submitted by Perry Baby 3/1/15.

Nell gives Perry a business card with her info typed on it. Important as a clue, but a bit ridiculous in real life. Business cards are normally printed - and if she did need to give additional info, it would have been far easier to hand print it rather than trying to run a business card size paper through a typewriter. DOD 07/15/18

Just after Ms. Gridley gives Mason her business card, the establishing shot of the town shows several cars driving by—but they are all from the 1930s or ’40s as well! Submitted by gracenote, 6/19/2011.

Speaking of cars, when Perry pulls his massive Caddy into Salty's gas station, he asks him to "fill it up for me." Unfortunately Salty had no hi-test gas, as he'd told Nell Gridley when she pulled up in her station wagon and asked for it. (In such a small town, wouldn't she have known that anyway?) Submitted by francis, 2/18/12.

+ Nell should be more careful about whom she asks to drive her station wagon. Pulling away from the gas pump in haste, Harry Bright almost knocks it down. Submitted by francis, 7/19/14.

If you want the pump while filling up Harry Bright's car, the level goes down in the reservoir! I believe these pumps worked by manually pumping gas up into the clear bowl and then drains into the car. Submitted by Perry Baby 3/1/15.

So we are asked to believe that Salty Sims was able to wait six weeks before telling Harry Bright, his neighbor across the road, that Chuck Clark was back in the neighborhood? Submitted by 10yearoldfan, 10 June 2012.
+ I was thinking the same thing. Kilo 10/28/2019.

The set decorators Walter Scott and Charles Vassar placed a nude female statue near Chuck Clark's front door. She is holding up a dish. Perhaps she symbolizes the young wife, begging for money. Submitted by 10yearoldfan, 10 June 2012.
+ Those statues must have been on sale. The same statue is next to the bar when Perry exits via the sliding glass doors. Submitted by Kilo 7/2/2017.

At 33:15 we see establishing shots of the county courthouse, the same courthouse used in Episode #45, The Case of the Buried Clock (but with different, also decades-old, cars out front). Note the Civil War era cannon in the park out front. Submitted by 10yearoldfan, 10 June 2012.

Goof: At 43:13, Perry shows Salty Sims the letter Salty had typed to Philip Morgan, supposedly proving that Salty had lied when he said he had never borrowed Nell Gridley's typewriter. But this letter shows a clean letter "n" unlike the dark ones in the phone number that Nell typed on the back of her business card and in the word "not" that Salty inserted into Morgan's letter. Perhaps the prop folks overlooked the word "investigating" that has the only "n" in the letter. Submitted by 10yearoldfan, 10 June 2012.
+ Being old enough to not only know what a typewriter is, but to actually have used several, I can attest to how it is next to impossible for a non-professional typist to reinsert and align a document to add a word to an existing line, even when using the same machine as the original, and not have it be readily apparent to even an untrained eye. Submitted by TerryS, 12/14/2018

Nell and Harry don't pay for their gas. Submitted by scarter, 8/10/14

Harry isn't too Bright. He's cleaning a loaded gun. Submitted by scarter, 8/10/14

Perry shows up in a rare light colored suit and tie during the second day of the trial. Submitted by Perry Baby 3/1/15.
+ And looks mighty fine in it, along with his tone-on-tone shirt and necktie! jfh 30Jul2019

A few continuity errors in the scene where Howard karate chops Harry from behind. First, it looks like this scene had multiple takes because Harry's pant legs are already dirty before falling down from the blow. When Harry fires the revolver at Howard's feet Howard takes several steps back. But the closeup showing where the bullet hit the ground shows it right next to Howard's foot. Lastly, up until Harry hits the ground he doesn't have a gun in his waist band. (DVD slo-mo catches this). Kilo 10/28/2019.