Blind Stealing
Q. A store in our area is completely run by a hired assistant who habitually steals from the till. I've hinted to the storeowner that closer supervision would be prudent, but he has complete trust in the assistant. Do I need to pursue the matter farther?
A. Let us review our general approach to informing on others. We need to balance our obligation to protect one party from damage with our prohibition to unfairly slander the wrongdoer. The Torah emphasizes this delicate balance by including both mandates in a single verse: "Don't go as a talebearer among your people; don't stand idly by the blood of your fellow; I am God" (Leviticus 19:16).
The general rule is that informing is proper when it is the only means of preventing a loss and doesn't cause unjustified damage to the wrongdoer.
Given this principle, you acted properly when your first comment to the storeowner didn't refer specifically to the assistant. If a general comment that close supervision is prudent were sufficient to cause the owner to make order in his business, then reporting the assistant's specific wrongdoing would be superfluous and therefore improper.
However, now you see that this general piece of advice has not helped rectify the situation. In this case, it is permissible to tell the owner about the specific misdeeds of the assistant, since this may help the owner stop further losses and perhaps even recoup past ones. The loss to the assistant is not undeserved since it is certainly appropriate for him to be held accountable for his irresponsibility.
A further comment is in order. "Don't stand idly by the blood of your fellow" is normally a Torah obligation, not a recommendation. Each person should show collective responsibility and protect others from loss or damage, as long as the effort is reasonable and commensurate. Yet we learn from another verse that our obligation to help others is just that: an obligation to help them, not to absolve them of responsibility for themselves:
The Torah tells us that if we see someone's pack animal stumbling under his load, we must "raise it up together with him" (Deuteronomy 22:4). Rashi explains why the Torah adds the words "together with him": "Together with the owner. But if [the owner] steps aside and sits down, saying 'Since the commandment applies to you, go ahead and load if you like', [the bystander] is exempt." The primary responsibility certainly lies with the owner; others are commanded to be helpful when they can.
In your case, the owner is not taking even normal minimal responsibility to supervise his store. Our Sages emphasized that when hiring workers, the responsibility for careful work is not only on the workers, but also on the owner to supervise them properly. They "advised" that someone who inherits a large fortune and wants to dissipate it rapidly should hire workers and neglect to oversee them. (1)
It's not fair for the storeowner to impose all the burden of supervision on well-meaning customers like yourself. So while it is ethical and praiseworthy for you to give more details about this crooked assistant, if you decide that you really don't want to get involved, your position is understandable.
SOURCES: (1) Babylonian Talmud Bava Metzia 29b.