A) He was arrested by police.
B) He had been arrested by police.
In newspaper reporter want to tell about past event that has already happened.
In above statements Reporter conveyed same meaning, that police have arrested criminal and he is still in there custody.
I am aware that above sentence are in past Tense i.e. former is in simple past and later is in Past perfect and also in passive voice.
My question is that why reporter purposely used was and had been in sentence? Instead of that he could have used present perfect. Example:
He has been arrested by police.
Also some times reporters does not use simple past before using past perfect.
He had been arrested by police when I was reached on the spot.