The point many have made here could be stated in this way - that God's existence is intuitively obvious in light of creation. However one's intuition is a function of one's spirit. You ask about the Holy Spirit. I think in cooperation with the Holy Spirit working in conjunction with one's own spirit, God's existence will become obvious.
It's like if you were on a desert island and you saw footprints in the sand you would infer someone made them even though you hadn't seen the person. Or better yet, if you examined leaves on a tree and found writing on them - information coded into a language form - encompassing volumes of information about the tree. You would naturally infer that someone must have wrote that information. It's intuitively obvious. And yet that is the case - with regards to the DNA code inherent in all life. Yet what is intuitively obvious to some, to others it's not intuitively obvious due to the difference in people's spiritual condition.
However as for forensic evidence validating the claims of Christ, I am ashamed that no one here has yet given the evidence that Christ provided. Namely his resurrection from the dead. When Paul was trying to convince the philosophical Greeks in Athens he said this, among other things, "now he commands all people everywhere to repent. For he has set a day when he will judge the world with justice by the man he has appointed. He has given proof of this to all men by raising him from the dead" Acts 17:31,32
Whenever the gospel is preached in the Bible, the resurrection of Christ is mention as forensic evidence validating the claims of the gospel. What I suggest is you read a gospel, like Luke or John, and see if it's convince to you.
Unlike other religions, the Bible doesn't expect you to believe on a purely irrational basis. But to believe on the basis of sufficient evidence that would be expected by any reasonable person.
