Can "Sola Scriptura" Protestants Authenticate the Bible?

I'm working on a case right now that looks like it may go to trial, and there is a potential issue regarding the admissibility of a document that I might try to offer as evidence. This issue involves authentication and it got me to thinking a little bit about the "Bible-only" approach to Christianity that many Protestants follow.

Within the lexicon of civil law, to "authenticate" a document during a trial generally means to establish its' claimed source of origin. For instance, any police report allegedly written by Officer Smith is inherently questionable and unreliable unless Officer Smith provides sworn testimony that he in fact wrote the report. Without this sworn testimony, no one can be certain as to whether Officer Smith really wrote the report or if it was just made up by someone out of thin air.

With this in mind, I'm geuninely curious as to how any non-Catholic Christian who subscribes to sola scriptura (i.e., there is no other authority for Christianity except the Bible) is able to authenticate the Bible. (The principle of self-authentication would not appear to be an option, since even that requires recognition of an external authority).