Joinder of independent defendants is only appropriate where the accused products or processes are the same in respects relevant to the patent. But the sameness of the accused products or processes is not sufficient.

On May 4, 2012, in In re EMC Corp., the U.S. Court of Appeals for the Federal Circuit (Rader, Dyk,* Moore) granted EMC's petition for a writ of mandamus to order the U.S. District Court for the Eastern District of Texas to sever and transfer claims to various other U.S. district courts in a case involving U.S. Patents No. 5,771,354, No. 5,901,228, No. 6,411,943 and No. 7,080,051, which related to off-site computer data storage. The Federal Circuit stated:

We must here address as a matter of first impression whether mandamus can be an appropriate means to test a district court's discretion in ruling on motions to sever and transfer. While transfer motions are governed by regional circuit law, motions to sever are governed by Federal Circuit law because joinder in patent cases is based on an analysis of the accused acts of infringement, and this issue involves substantive issues unique to patent law. We thus apply Federal Circuit law to determine the availability of mandamus, and to the underlying issue of whether the motion to sever should be granted....

We conclude that mandamus is available as a remedy. With regard to the "no other means" requirement, there is no meaningful distinction between a petitioner's seeking review of an order denying transfer because the district court clearly abused its discretion in applying the § 1404(a) factors and a petitioner's seeking review of an order denying a motion to transfer because the district court clearly abused its discretion by not severing the claim as a predicate to determining whether to transfer. In either case, a defendant would not have an adequate remedy for an improper failure to transfer or sever the case by way of an appeal from an adverse final judgment because the defendant would be unable to demonstrate "that it would have won the case had it been tried in a convenient [venue]."...

We turn to the issue of severance. We first note the unusual circumstances from which this petition comes before us. Recently, Congress addressed the issue of joinder in patent cases in section 19 of the Leahy-Smith America Invents Act, which was signed into law just days after this petition was filed. While petitioners argue that joinder here would be improper under the new and old rules, they wisely refrain from arguing that the new 35 U.S.C. § 299 itself mandates this outcome. As a general rule, we do not give statutes retroactive effect "unless Congress clearly indicates its intention to do so." This new provision is not retroactive, applying only "to any civil action commenced on or after the date of the enactment of th[e] Act." The timing of this petition means that our decision will only govern a number of cases that were filed before the passage of the new joinder provision....

It is clear that where defendants are alleged to be jointly liable, they may be joined under Rule 20 because the transaction-or-occurrence test is always satisfied. But the language of Rule 20 makes clear that joinder is not limited to such situations. Defendants may be joined if "any right to relief is asserted against them jointly, severally, or in the alternative," so an allegation of joint liability is not required. . . . In imposing both the transaction-or-occurrence requirement and the requirement of a common question of law or fact, Rule 20 makes clear that the existence of a single common question of law or fact alone is insufficient to satisfy the transaction-or-occurrence requirement. In the present context the mere fact that infringement of the same claims of the same patent is alleged does not support joinder, even though the claims would raise common questions of claim construction and patent invalidity. . . . Thus, independent defendants satisfy the transaction-or-occurrence test of Rule 20 when there is a logical relationship between the separate causes of action. The logical relationship test is satisfied if there is substantial evidentiary overlap in the facts giving rise to the cause of action against each defendant. In other words, the defendants' allegedly infringing acts, which give rise to the individual claims of infringement, must share an aggregate of operative facts. . . . Where different products or processes were accused of infringing the same claims, the "not dramatically different" standard would inevitably be satisfied. The petitioners here point out the difficulties that would be presented by joinder of claims involving "different" products or processes, and point to cases outside the Eastern District of Texas that have refused joinder where the products or processes are "different."

We agree that joinder is not appropriate where different products or processes are involved. Joinder of independent defendants is only appropriate where the accused products or processes are the same in respects relevant to the patent. But the sameness of the accused products or processes is not sufficient. Claims against independent defendants (i.e., situations in which the defendants are not acting in concert) cannot be joined under Rule 20's transaction-or-occurrence test unless the facts underlying the claim of infringement asserted against each defendant share an aggregate of operative facts. To be part of the "same transaction" requires shared, overlapping facts that give rise to each cause of action, and not just distinct, albeit coincidentally identical, facts. The sameness of the accused products is not enough to establish that claims of infringement arise from the "same transaction." Unless there is an actual link between the facts underlying each claim of infringement, independently developed products using differently sourced parts are not part of the same transaction, even if they are otherwise coincidentally identical.

In addition to finding that the same product or process is involved, to determine whether the joinder test is satisfied, pertinent factual considerations include whether the alleged acts of infringement occurred during the same time period, the existence of some relationship among the defendants, the use of identically sourced components, licensing or technology agreements between the defendants, overlap of the products' or processes' development and manufacture, and whether the case involves a claim for lost profits. The district court enjoys considerable discretion in weighing the relevant factors.

In exercising its discretion, the district court should keep in mind that even if joinder is not permitted under Rule 20, the district court has considerable discretion to consolidate cases for discovery and for trial under Rule 42 where venue is proper and there is only "a common question of law or fact." Common pretrial issues of claim construction and patent invalidity may also be adjudicated together through the multidistrict litigation procedures of 28 U.S.C. § 1407. On the other hand, even if a plaintiff's claims arise out of the same transaction and there are questions of law and fact common to all defendants, "district courts have the discretion to refuse joinder in the interest of avoiding prejudice and delay, ensuring judicial economy, or safeguarding principles of fundamental fairness." In a complicated patent litigation, a large number of defendants might prove unwieldy, and a district court would be justified in exercising its discretion to deny joinder "when different witnesses and documentary proof would be required."