The phrase "fact about which" is grammatically correct and can be used in written English.
It is typically used as part of a complex sentence to introduce a clause that provides additional information or context about a fact mentioned in the main clause. Example: The scientist presented a theory, the fact about which had been extensively researched and supported by numerous experiments. In this example, the phrase "fact about which" introduces the clause "had been extensively researched and supported by numerous experiments," which provides more information about the fact mentioned in the main clause (the scientist's theory).
The undercovers are almost all black or Latino, a fact about which they are pragmatic.
But ultimately the society is the winner here, a fact about which its more active members are no doubt aware.
This is a fact about which I have direct evidence without having to read a government-commissioned report.
The Times quoted another source who simply said: "Dave lost," – a fact about which it seems at least one Government contact was not best pleased.
Kanye West has won 18 Grammys, but they have all been in the rap field, a fact about which he has complained publicly.
It is rather because we are developing an increasingly large, illiterate, and generally unemployable underclass - a fact about which income transfer programs alone can do nothing.
When the police rely on facts about which they have personal knowledge, requiring them to disclose those facts to magistrates imposes no significant burden on the police.
These bare facts (about which Yelland is publicly candid) elicit conflicting responses, as does this, his first book for children, which is quasi-autobiographical, heartfelt and expiatory.
Mr. Helmstetter brims with facts about which plans are popular ("Get Breast Implants") and which fall flat ("Become a Professional D.J").. "I don't want to get into social engineering," he said.
If the federal claims (and possibly the Maryland claims) stay in, then the Federation would likely be able to argue that the Center people's refusal to testify should be counted against the Center (so long as the facts about which the Center people refuse to testify are relevant to the federal or Maryland claims).
When Danton meets with Robespierre to discuss his fate, he at first tries to tease his friend out of his fantasy of purity ("I'd be disgusted with myself if I spent thirty years with such a self-righteous expression stuck on my face"), then to reason with him ("Purity needs vice, if only for contrast"), and, finally, to draw his attention to the facts about which Robespierre has befogged his mind.
