I do remember a brother whose inactive JW wife had divorced him but not on scriptural grounds. He and an elder staked out her house and took a videocam and filmed her with her boyfriend at the house after 2 a.m. Based on that, she was DF'd and he was able to remarry the sister he already had in the wings.
I know of other elder duos who have staked out people's homes to catch them in wrongdoing as above, such as smoking.
There are some nasty ones out their guys. It is hard to imagine it if you would never do it. They would never tell the "good" elders and would make sure these "good" elders aren't on the judicial committee.
Some elders do think they are "spiritual policemen."
w758/1p.474All the elders should appreciate their position in relation to the other brothers and sisters in the congregation. They are not spiritual bosses or spiritual policemen. They do not have to pry into the lives of other members of the congregation or concern themselves with the personal problems of every brother and sister.
w769/15p.563Yet Jesus said that no one was good except God. (Mark 10:18) So he was not "righteous overmuch" so that he found fault or looked for faults in his disciples, as a ‘spiritual policeman.’ (Eccl. 7:16) Neither did he burden or discourage them, in a Pharisaical manner, making their consciences feel bad by demanding perfection of them.