While reading some of the comments above, I remembered two remarkable incidents that occurred when I was still a JW back in the 1960s. Both of these cases happened in southern California, but in two different congregations.
One brother who was an active pioneer in the Riverside Congregation was arrested for DUI. After spending a few hours in the local jail, he was released with no bail. A sister who worked as a records clerk for the police department (she was given a pass on this by the elders since she was not a "gun-toting police officer") saw the arrest report and called the congregation servant. At the next meeting at the Kingdom Hall, the accused brother did not show up, but the gossip about him and his arrest was all over the Kingdom Hall and, of course, he was assumed to be guilty.
When the brother did not show up for the next service meeting, there was an announcement made that anyone having contact with the accused should call the CongServ. Everyone figured that the accused brother was guilty and was destined to be tried and DF'd forthwith. The only information the elders had was that reported by the sister working at the police station.
A couple of weeks later my father told me that the accused brother had been cleared and WOULD NOT be reproved, placed on probation, or DFd for drunkeness and for bringing shame on the congregation. It turned out that the brother had a blackout while driving due to diabetes. Yes, he had been drinking, but was well under the legal limit (which at that time was 1.0, not the 0.8 that it is now in most states). While the alcohol may have contributed to the event, it was not the cause. The reason that he had not been to meetings was that he had himself hospitalized for treatment - and it was only then that he discovered the cause of his blackout. He was shocked and embarrassed that everyone thought he had been guilty of a crime. After that he was on insulin as long as I knew him and he eventually left the Kingdom Hall and never returned.
The point is, of course, that the sister should never have shared that confidential information. She had no right and broke police department rules. She obviously knew that, but did it anyway. And, of course, the elders took no action against her.
The second case involved the West Hollywood KH in the late 1960s. One of the sisters in the congregation had to have a cesaerean delivery and during the operation she began to hemmorhage. Apparenty everything happened so fast, the the medical team just started giving her blood to stabilize her condition and to save the baby. Her husband was not a JW. A JW sister was working in the hospital at the time, but was not directly involved as part of the medical team. I'm not sure, but my guess is that she was working on the same floor, or at the desk, and learned of the case after the fact. The first call she made was to the congregation servant. The sister was subsequently brought before a committee and charged with voluntarily taking a blood transfusion. She pleaded that she was under anethesia and did not have a believing husband or other JW relative with her at the time. So the doctors treated it as an emergency and took the action they felt was necessary. Although I was not a JW at the time, my wife (who was) told me that they decided to DF the sister anyway, since she had not made it clear before going into surgery that she was a JW and did not want blood. This was in spite of the fact that the doctor and the hospital administrator wrote a letter in her defense saying that in order to save her life (and also to avoid a costly lawsuit) they arbitrarily made the decision to give her blood. She survived and so did her baby, so obviously they made the right decision. They even mentioned in the letter that it had as much to do with their consciences as hers, and they could not just let her and her baby die without taking action.
But again, no one would have known except for that JW nurse who took it upon herself to report this case to the elders. Even then, in the late 1960s, I'm sure that patients had some privacy rights. According to my then JW wife, the sister just told the elders where they could stick their DF and went off and enjoyed the free and wild Hollywood scene with her unbelieving husband.
So I know personally that JWs in critical jobs are willing to break confidentiality and privacy rules in order to report errant JWs - guilty or not.