Infringer's Profits as "Residual Damages" Under German Law

On a couple of occasions I have blogged about Restschadensersatz, or residual damages, under German law (see here and here).  More precisely, in 2013 I wrote:

In Germany, the statute of limitations for filing an action for patent infringement is governed by article 141 of the Patent Act.  WIPO’s translation of this provision reads:

As regards the period of limitation for claims due to infringement of a patent right, the provisions of Part 5 of Book 1 of the Civil Code shall apply mutatis mutandis. If the infringer has gained something through the infringement at the expense of the entitled party, Section 852 of the Civil Code shall be applicable mutatis mutandis.

Focusing on sentence 1, the general statute of limitations for filing a patent infringement claim is three years.  See Thomas Kühnen, Patent Litigation Proceedings in Germany:  A Handbook for Practitioners ¶ 1554,at 389 (6^th ed. Frank Peterreins tr. 2013); Benkard, Patentgesetz § 141 ¶ 4, at 1504 (10^th ed. 2006).  But the second sentence provides a second opportunity to file a claim for damages, after the three-year period has lapsed.  Here is the text of the referenced section of the Civil Code (BGB § 852) (English translation can be found here, German original here):

If by a tort the person liable to pay compensation obtains something at the cost of the injured person, then even after the claim to compensation for the damage arising from a tort is statute-barred he is obliged to make restitution under the provisions on the return of unjust enrichment. This claim is statute-barred ten years after it arises, or, notwithstanding the date on which it arises, thirty years after the date on which the act causing the injury was committed or after the other event that triggered the loss.

So even after the three-year period, the patent owner may get to file a claim, but for what?  The term used for the damages the patent owner may recover under these circumstances is Restschadensersatz, or residual damages.  Prevailing opinion is that these damages consist of a reasonable royalty only.  See Benkard Patentgesetz, § 141 ¶ 6, at 1505-06.  The argument appears to be that the only benefit the infringer derived at the expense of the entitled party is the royalty it didn’t pay.  For a contrary opinion, however, see Matthias Hülsewig, Der Restschadensersatzanspruch im Patentrecht—beschränkt auf die angemessene Lizenzgebühr?, GRUR 2011, 673, arguing that the patentee should have the option of recovering the infringer’s profit or a reasonable royalty.

Then in 2016 I wrote:

A few weeks back Dr.  Hülsewig kindly emailed me a copy of a 2015 opinion of the German Federal Supreme Court in a copyright matter, in which the court states that the question of whether BGB § 852 permits the recovery of the infringer's profit remains an open question.  See paragraph 34 of Judgment of Jan. 15, 2015, I ZR 148/13 (BGH)--Motorradteile, available here.  In addition, as Dr. Hülsewig pointed out, the new 11th edition of the Benkard treatise on German Patent Law now also takes the position that claims for residual damages are not limited to reasonable royalties but also may include the disgorgement of other pecuniary benefits the infringer has derived ("Daher kann der Rest-Schadensersatzanspruch nicht in jedem Fall auf die (stets geschuldete) angemessene Lizenz beschränkt werden; vielmehr können auch weitere Vermögensvorteile herausverlangt werden" (section 141, p. 1907).  So perhaps we are witnessing a change in the majority view of what claims for residual damages may include under German law.

Well, it looks like the change in the majority view is now complete.  Two weeks ago Dr.  Hülsewig emailed me the BGH's Judgment of March 26, 2019, X ZR 109/16--Spannungsversorgungsvorrichtung ("Power Supply Device"), in which the court definitively holds that the patentee can demand the disgorgement of the infringer's profit as residual damages.  As my previous blog posts on the subject suggest, I'm not convinced this is a great idea as a matter of policy, but the doctrine now appears to be settled.