If the defendant voluntarily discloses to authorities the existence of, and accepts responsibility for, the offense prior to the discovery of such offense, and if such offense was unlikely to have been discovered otherwise, a downward departure may be warranted. For example, a downward departure under this section might be considered where a defendant, motivated by remorse, discloses an offense that otherwise would have remained undiscovered. This provision does not apply where the motivating factor is the defendant’s knowledge that discovery of the offense is likely or imminent, or where the defendant’s disclosure occurs in connection with the investigation or prosecution of the defendant for related conduct.