A split patent litigation system is one in which infringement and validity are tried in separate cases. The best known split system is Germany.
Thus in German patent litigation infringement is a separate case from validity. The infringement case is brought in the state or lander courts (Landgericht) while validity is challenged in the Federal Patent Court (Bundespatentgericht.) The Landesgericht, particularly in Düsseldorf, will usually reach an initial decision on infringement much more quickly than the Bundespatentgericht reaches a decision on validity. The Landgericht can issue an injunction even if a validity proceeding is pending but it may be persuaded to stay the injunction if it believes the non-novelty case to be strong. Appeals of both validity and infringement continue through separate court systems until they reach the Federal Court of Justice (supreme court for non-constitutional issues) or Bundesgerichtshof.
Most notoriously, based on various jurisprudential arguments (that non-German lawyers generally find at least surprising, and often unintelligible), a party can in principle be permitted to advance different claim constructions in each court system regarding claim construction, avoiding the so-called squeeze argument. The English Lord Justice Jacob famously and sarcastically refers to the issue as the Angora Cat problem:
“When validity is challenged, the patentee says his patent is very small: the cat with its fur smoothed down, cuddly and sleepy. But when the patentee goes on the attack, the fur bristles, the cat is twice the size with teeth bared and eyes ablaze.”