There are many such stories and many which are resolved without resort to the Ombudsman.

There are some common threads.

If you have a record, don't be dismissive or judgmental. But, do make certain that you have attested (certified) copies of the paperwork showing a final disposition of the case.

This is a very common problem with seemingly minor offenses. Because they were continued without a finding or whatever process a given state uses, nobody ever entered a final disposition and the criminal history record that CBP sees just shows the matter as "pending" years later. For all CBP knows, you might have skipped out on a jail sentence or have an unpaid fine. So, the final disposition showing that the case is closed is critical.

If you have an offense which was sealed or has some other disposition short of a conviction under some local law, that likely does not mean anything to CBP. You have an opportunity to explain yourself, but do not try to play cute. Just answer the questions. If you are asked about an offense which did not result in a conviction, explain the situation, but do not simply deny it.

Don't be dismissive. If you want to make a joke about a "small amount of pot" do it with some friends. You don't know how a federal law enforcement officer will take your attitude and if he takes it wrong, you are SOL. Your GE interview is not a social occasion, so treat it seriously.