Pursuant to Labor Code § 5500.5(a), liability for a cumulative trauma (CT) injury is limited to the employer(s) that employed the worker during the one-year period immediately preceding the date of injury (LC 5412, or the last date of injurious exposure, whichever occurs first. That means multiple employers or insurers can be liable for a CT injury.
For cases in which multiple defendants have liability for a CT claim, LC 5500.5(c) allows the applicant to elect against any one or more of them. If the applicant makes an election against a defendant, he or she is required only to prove the claim against the named defendant. Liability for the nonelected defendant isn't determined until supplemental proceedings are instituted. Only the elected defendant has complete discovery rights, and the rights of nonelected defendants are deferred to contribution proceedings.