Nobody can know for certain if another person has the Holy Spirit.
In all 4 of the examples recorded in the bible (Acts 2, 8, 10, 19) It was clearly stated at what point those people received (or had NOT yet received) the Holy Ghost. And in all 4 there was an attribute that was immediately observable to those around.
The parts of belief, repentance and intents of the heart might remain hidden until revealed by God or by the later behaviors and fruits of the individual, but the Holy Ghost comes 'bearing witness'.
Love in Jesus,
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