Fine in lieu of forfeiture allows payment of market value for an unproven portion to prevent property forfeiture. Where a court declares property forfeited but only part of its source is unproved, the person affected may be offered the option to pay a fine equal to the market value of that unproved part instead of forfeiture; the person must be given a reasonable opportunity to be heard, and on timely payment the court may revoke the forfeiture declaration and order release of the property.