By what specialized method was concluded to determine the Bible is given by God, besides the Bible's say-so?
By a method which is unknown to humans but they use this method all the times without their own awareness.
Now tell me what you yourself did on May 23 2015?
Not one out of the 7 billions humans on earth can somehow answer this questions. Simply because evidence of that day of your deeds and speeches don't exist. This is true especially before the invention of photos and videos. Strictly speaking, photos and videos are not evidence but testimonies in a more reliable form, their dates and contents can still be faked.
Now what method can be used for us to possibly get to what you did on May 23 2015? If an eyewitness (or yourself) wrote it down what you did (or better tape it down) for us to believe with faith. That could possibly be the only way (if not the only way, it remains the most efficient way) for us to get to know what you did that day.
Everything else boils down to how reliable and credible this eyewitness is. The NT Bible was written/compiled/crafted by those claimed eyewitnesses who were willing to martyr themselves in order for their testimonies to spread.
Human witnessing is an exclusive method for humans to reach a truth of any kind. The so-called "evidence" is a joke. You are brainwashed by secular education since childhood to think evidence is the way how humans determine a truth/fact while it's not! The more fundamental way for humans in majority to determine a truth is by faith! (believe it or not).
99.99% humans don't even bother to examine the evidence that earth is actually revolving around the sun (a scientific truth). We put faith in that our scientists (as our eye-witnesses) won't be mistaken about this. They are the reliable and credible eye-witnesses.
When you watch TV for daily news, you don't dig up evidence behind each piece of news. Instead you rely on our media which is made of reports and journalists as eyewitnesses to reach each and every piece of facts. This is so because our media is thought to be reliable and credible.
Now you have the following,
1 History (such as what you did on May 23, 2015) is unreachable directly to humans. We can't verify distant history under most circumstances (believe or not, if not pick any history and count which page is supported by evidence).
2 Science (such as earth revolving around sun) is reachable by us as science is all about a repeating phenomenon. It repeats indefinitely for us to acquire evidence anytime we wish to. However, somehow 99.99% of us don't bother to do so. We'd rather put faith in our scientists to trust that they have the evidence.
3 Today's occurrence (such as TV news) can be reachable by us as they are freshly happening. You can always go to the Royal Wedding by yourself instead of trusting what is broadcast. Yet 99.99% of us choose to sit home without gathering any evidence but putting faith that our media is faithfully telling the story.
Do you have any other truths which don't rely on faith to convey? How about the future?
Humans are more futile about the future (than the history such as what you did on May 23, 2015). The only possible way for humans to reach what could possibly lying ahead is, again, by putting faith in human accounts of witnessing. They are liars or not, it's the only possible way for us to possibly get to a truth of our future.
Future is unreachable to humans directly. However if God exists and tells our future to His chosen eyewitnesses (by a coincidence, in Christianity all OT prophets are called God's witnesses), we can thus reach such a truth by putting faith in those witnesses.
So it all boils down to how reliable and credible those claimed eyewitnesses are? I bet that you can't make it more credible when they choose to sacrifice their own lives in order to bring the message out.