On what basis can a plaintiff claim statutory damages for copyright infringement?

The plaintiff can can claim statutory damages if he 1) prevails in the lawsuit, and 2) has registered the work prior to the infringement lawsuit. In this situation, the copyright owner can choose whether to seek statutory damages or actual damages anytime before the final judgment. The decision typically depends on the amount of actual damages and the ability to proof and document them. For instance, if the actual damages can be easily demonstrated and these are significantly higher than the maximum statutory damages award, the plaintiff would likely be advised to seek actual damages. In both cases, the copyright owner sustains the burden of proof regarding the degree of the damages and willfulness. Despite the fact that intent is irrelevant for proving infringement, it is often an important factor to determine the award of statutory damages.

At the time of this writing, statutory damages for infringing a single work range from $750 to $30,000. However, the court may increase the award at its discretion up to $150,000 in cases of evident willful infringement. Similarly, if the court concludes that an infringement was innocent it also has discretion to reduce the statutory damages to a minimum of $200. These amounts are multiplied by the number of works infringed. In addition to the statutory damages, the loosing party may also have to pay all the attorney fees if the copyright owner registered the work prior tot he infringing activity.

References:
[1] Stim, R. "Intellectual Property. Patents, Trademarks, and Copyrights" West Legal Studies.
[2] Black's Law Dictionary 5th ed., (West Publishing, 1979).
[3]
Copyright Act of 1976