Despite being touted as a cliche, there's actually not a lot of times where the butler really did it-at least in literature. In fact, we don't even really know where the trope, or phrase itself (if it was ever actually said) originally comes from.
The majority of the examples of it are from long after it was supposedly created, and even then, most of these examples are parodies, or just don't play it straight in general, and both works that are frequently cited as being the origin of it (1930's The Door, and 1928's Twenty Rules for Writing Detective Stories, respectively) don't actually say the line, and in the case of the latter, explicitly state for the butler to not be the culprit because that would be too obvious.
The most likely theory is that the exact origin doesn't come from books, but instead from movies because while the butler doing it isn't common in literature, it was common in silent films for a time as there's a quite a few where it, or something very similar to it happens.
Notably, the majority of these movies were all made within the same ten years (specifically from 1915-1925), and considering how the trope was already considered a cliche by the early 1920s, this could very well be the answer.
However, another interesting thing worth mentioning is that a good chunk of those films that are said to have it are now considered lost, so it is entirely possible that one of them actually has the line word-for-word, and we just can't verify it because it's now next to impossible to do so.