Here is an example of a demon possessed woman. She has been deceived by a religious devil.
In this case, I would cast out the demon when spiritually strong so that she can be led to the true Jesus.
https://www.allthepreaching.com/pages/video.php?id=9871536
In this state of being, she is under control of the demon and might not even be conscious of it.
I was attacked by a demon that entered the body of a petite 18 year old lady at WVU. It tried to kill me and but for the Lord's protection, surely could have. Inbetween attacks it mumbled in what sounded like an ancient foreign language that I never heard. I wish that it was video recorded so I could share it with others. I have her picture that Mom decided to save since she was my girlfriend in college.
I tried to no avail trying to reach Maria/ Mary S. Later when I cast it out, she acted as if torn within. It wouldn't let her hear. It took over all her physicality/ senses and body.
It spoke to me many times in the strange language. The Bible speaks about how they murmer.
It's a long story of an important event that is due strong consideration.
Very few believers are ever attacked by a demon, more or less one that is in combat mode, turning off the person's governor so they are a human weapon attacking with whatever objects can be used as weapons . It/ they (however many I don't know) tried to stab me, crush my skull and rip out my eyes!
These are not creatures like the YouTube "deliverance ministers" make them out to be. I've seen some hold out their giant cross as if they were in a vampire movie. Then people get the idea that they can do the same.
What they really need to do is to get the power of God, get strangers saved so they can more easily lead family to Christ.
When it eventually was cast out, she became immediately unconscious.
She woke up out of breath gasping and panting for air, sweating, looking around Wondering where she was and how she got there.
When I told her, she didn't believe me at all.
If I were you and you thought he was demon possessed, I would take a SAVED known pastor who has been leading others to Christ for years. I can give good examples. You can assist as he directs. Demons are dangerous creatures that should not be taken lightly like the phony TV preachers make them out to be. They murder people for joy and seek to harm beyond a normal person's ability to conceive.
If your pastor teaches that you can do good works to be saved, I would find another. Once you have the gift of everlasting life, you are saved for life everlasting. Anything else leads to fear and torment. The sons of Sceva in the Bible taught obedience to Old Testament law, aka repent of your sins (turning from disobedience to the law) as the way you get saved. Their clothes were torn off their bodies and sustained series injuries.
They were in their deliverance ministry trying to cast out devil's without God's power and presence.
13Then certain of the vagabond Jews, exorcists, took upon them to call over them which had evil spirits the name of the Lord Jesus, saying, We adjure you by Jesus whom Paul preacheth. 14And there were seven sons of one Sceva, a Jew, and chief of the priests, which did so. 15And the evil spirit answered and said, Jesus I know, and Paul I know; but who are ye? 16And the man in whom the evil spirit was leaped on them, and overcame them, and prevailed against them, so that they fled out of that house naked and wounded. 17And this was known to all the Jews and Greeks also dwelling at Ephesus; and fear fell on them all, and the name of the Lord Jesus was magnified.
However, the Lord supernaturally brought me directly to the exact verse of His power. Luke 11:20
20But if I with the finger of God cast out devils, no doubt the kingdom of God is come upon you.
-Jesus