Like Murder Most Foul (1964), this movie was adapted from an Hercule Poirot novel ("After the Funeral"), not a Miss Jane Marple novel.
Miss Jane Marple (Dame Margaret Rutherford) refers to a "remarkable novel" of Dame Agatha Christie's, "The Ninth Life." This was an in-joke; her creator wrote no such book.
Stringer Davis (Mr. Stringer) was Dame Margaret Rutherford's husband. The part of Jim Stringer was created for him, and never appeared in any Christie novel.
The world première took place at a church garden party in rural Cheshire, England.
When reporting the second murder to the police on the phone, Miss Jane Marple uses the phrase "murder most foul." A quote from William Shakespeare's "Hamlet" (Act I, Scene V (lines 27-28): "Murder most foul, as in the best it is;/But this most foul, strange, and unnatural."), it was reused as the title of the following Miss Marple movie.