Not unrelated: I guess the obligation to declare bribes as income allows the IRS to investigate you for tax evasion if they suspect you're receiving (obviously undeclared) bribes.

Actually if you declare the income and classify it correctly you are clear from an income oersoective; by disclosing the crime you risk confiscation and prosecution but neither would involve the irs beyond certification of your submissions. Source: armchair cpa

But isn't that the point? If you don't declare the crime you're liable for tax evasion and can be prosecuted by the irs; if you do, you're going to be prosecuted by a different authority. And since nobody is going to self-incriminate, when they catch you you'll be prosecuted both for corruption and tax evasion.