Here is how I see it. Bear with me a tad as it is somewhat complicated:
I do believe there will be a heart change when a person is saved, and do believe many think they are saved because they believe the bare facts and did whatever their particular church culture says you do when you get saved, but are not saved.
That said, I also know God labelled the adulterous David a man after God's own heart. He said the miserable sinner who prayed for mercy went home justified, not the Pharisee who was intent on thanking God he wasn't a sinner like others were. Jesus spoke of tax collectors and prostitutes entering the kingdom ahead of the righteous folks.
Jesus said if anyone come to Him He will in no wise cast him out. So I figure the rottenest sinner, if truly trusting only in the shed blood of Christ to save him will be saved. It will show, if only to God. He may have a vile temper and rage and curse, but God may know that unsaved he would have been a serial killer. God is in control of that man's sanctification process and speed, and I best keep my nose out of it.
I wouldn't go around judging the condition of another person's soul. Rather I would focus on my own walk of obedience, and let the Holy Spirit work in their lives. Rather than judging them worthy of hell, I might pray to the Lord on the basis of loving them and being concerned for them.
Share Christ and salvation with all, work on your own life, trust and take Jesus at His word. We are saved only by the blood, not by our walk. As to it showing, it should, but beware of being a Pharisee. That would show YOU have not trusted only in the Blood.