Everybody’s heard an urban myth, you’ve probably even repeated one thinking it’s true.
Well they’ve been with us for a long time. Some persist and some no doubt fade away.
One which once was very prevalent years ago, but is unheard of now (even amongst academics) is the myth that if you’ve witnessed an incident through a window then your evidence is inadmissible in a court of law.
This article is from the Birmingham Daily Gazettein 1928.
Have it found his surprising story I searched the archives for further examples.
Northern Daily Telegraph 1906.
Lincolnshire Echo 1945.
It appears this had been a longstanding myth, now forgotten. An article from 1896 (Weekly Irish Times) calls it an ancient belief and offers an explanation as to why it may have originated.
As for the question on if there’s any truth in the myth, and if at one point in history this may have been a rule, so far I’ve found nothing.