The knife Perry has Roan Daniel identify on the witness stand is the same knife used by Mignon Germaine (Fay Wray) in her nightclub act - and which was the murder weapon - in The Case of the Fatal Fetish (1965).
This also was Dan Tobin's first appearance as restaurant owner Terrance Clay. Clay's restaurant/bar would act as a neutral ground for Mason and Burger to hang out in for the remainder of the series' run.
Last screen appearance, TV or film, of John Dall and one of his four appearances on Perry Mason.
While this ninth season made Perry Mason one of the longest-running drama series in TV history up to that time, the Nielsen ratings had by now diminished to the point where it made sense for CBS to cancel it at season's end. From a series high of ranking 5th among all shows being aired in its fifth season, for its final year, Mason tumbled all the way down to 69th place.