When Dan Southern (Adam West) checks the registration for Fred Swan's car, the address shown is 1040 No. Las Palmas. This is the address of the General Services Studio, where some of the episodes were filmed.
Ms. Sarah's old car is a 1940 Packard.
Most of this episode involves an out-of-town investigation conducted mainly by Paul Drake, whereas the hearing involving Perry Mason is quite short. Thus, William Hopper has more screen time than Raymond Burr (but Burr still has more lines). Burr delivers some of his lines as though he has a respiratory infection; it may be that he was ill, and some of his scenes were reassigned to Hopper.
In the courtroom scene, the "Ironside" window appears. This now famous window appears in several Perry Mason episodes.
A sign for the Pinon City Founders Week shows the celebration took place from July 7 through 14, so much of the first half of the story takes place then. The preliminary hearing, though, is sometime after July 14, because Alfred Needham has shaved his beard, Dan Southern has trimmed his sideburns, and W.L. Picard is no longer wearing western ties - which they donned for the celebration. The sign also shows that Pinon City is celebrating its 75th year. Assuming the episode takes place in 1960 (the episode first aired in March 1961, before the July dates that year), Pinon City was founded in 1885.