Update: thank you everyone! user @Today has provided a great link of a discussion that suggests the correct answer is where being an abbreviation of, whereas as a replacement of since, hypothesized in these comments.
As I love archaic definitions, I’m more convinced to now that this is the answer!
Especially since the question originates from one weirdo using “where” instead of since.
https://english.stackexchange.com/questions/338694/is-it-ever-appropriate-to-use-where-instead-of-because-or-since
Like “Where we knew he was heading to Chicago tomorrow, we got on the first plane heading east to intercept.”
“Where we knew where the safe was, we began to cut through the wall in the corner behind her desk.”
Thanks
It sounds like maybe something that comes out of legal jargon to my ears (disclaimer, I am no lawyer or anything of the sort, most of my understanding of lawyer talk comes from tv shows and movies which are not usually the most accurate)
I could kind of imagine some sort of statement beginning with something like “Where the defendant, having been…” followed by some descriptions of circumstances and legal precedents and such.