Just before this episode was shot, William Talman injured his right leg and was fitted for a cast. The writers had no choice but to work this into the script--Hamilton Burger wears a cast and ambles about on crutches throughout the episode.
This plot is closely related to the Erle Stanley Gardner Perry Mason book "The Case of the Careless Kitten." The TV show sometimes took parts of one ESG book and used them to create multiple shows.
In this episode, evidence exhibits are assigned numbers, not letters as in other episodes.