だって事実だろ。

[ericaw]

English Translation

But it’s true.

Does だって function as a " but"?

[MsFixer]

@ericaw
Interesting question! だって is a simple word we frequently use in a daily conversation. But I’ve never thought about the meaning.
The closest meaning would be “the reason is…” (interchageable with その理由は、). Here is a typical situation you can use the phrase.

Mary: Why do you say like that (e.g. terrible/harsh thing)? = なんでそんな（酷い）ことを言うの？
Tom: The reason is… That’s the truth. Period. = だって、事実だろ。

I support the author of the original translation in this context. The connotation of Mary’s is “you shouldn’t have said like that”. And Tom made a counterargument. So, the conjunction in English is “but”.

Please keep in mind that だって is very colloquial. It depends but it sometimes sounds a bit childish.

Angry Mom: Why did you have snacks before dinner? = なんで夕飯前にスナック菓子を食べたの？
Boy: Because I was hungry. = だって、お腹が空いてたんだもん。