That seems to me as a matter of style, where I would choose the first example and use the past perfect.
When you talk about past events, you may want your to convey, that one of these past events you mention actually took place prior to the other past events.
Attempting to mimic the OP example:
I got into the bedroom and I saw my wife under the bed. She was stabbed to death.
I got into the bedroom and I saw my wife under the bed. She had been stabbed to death.
The simple past version describes the past events unfolding in a chronological order, which the narrator wants them revealed in.
The past perfect version also reveals them in chronological order, but differentiates the last event mentioned, as having taken place before the other past events happened.
In the OP's simple past example it is pretty clear from the context, that the stabbing happened prior to the arrest, but you could use the past perfect version instead to indicate this even further.
Modern fiction makes extensive use of the simple past because it gives a strong sense of the action unfolding as you read. When you utilize the past perfect, it conveys the feeling, that the action have already taken place and now you are reading about it.