The adjuster on the other side of the mediation already knows about your client's 2019 rear-ender and the workers' comp claim from the warehouse job. The prior-claims report was pulled before the demand letter was even opened. So the question at mediation is never whether the defense knows — it is whether you got to the history first, on your terms, or whether the mediator carries it into your caucus as a surprise that just knocked six figures off the number in the other room.
Prior personal injury claims are the most predictable soft spot in a plaintiff's case and the one most often mishandled in the two weeks before a mediation. A history of claims is not a legal defense to anything. Treated correctly, it is a documentation problem. Treated as something to bury, it becomes a credibility problem, and credibility is the entire currency of a mediation where liability is not seriously contested.
Get the Disclosure Question Right Early
Start with what you actually owe. California's discovery scope under Code of Civil Procedure section 2017.010 reaches any non-privileged matter relevant to the subject of the action, including prior claims and prior treatment of the same body part. When your client puts a body part in controversy, the patient-litigant exception in Evidence Code section 996 strips the physician-patient privilege for records bearing on that condition. That means the cervical MRI from the earlier crash is coming in, and interrogatory responses asking about prior accidents and prior claims must be answered straight.
The failure mode is not usually a deliberate lie. It is a client who forgot the 2016 slip-and-fall that resolved for four thousand dollars, or who did not think a comp claim counted as a "lawsuit." A verified discovery response that omits a real prior claim hands the defense an impeachment exhibit that survives every good thing about your case. Run an index search and a lien search on your own client before you verify anything. Pull the prior claim numbers, the body parts, the settlement amounts if available, and the prior counsel. The same records discipline that protects a lien-heavy file protects the history — the workflow we describe for running the paralegal desk on lien-heavy files is the one that surfaces a forgotten claim before opposing counsel does.
Distinguish disclosure obligations from mediation confidentiality. Whatever you say inside the mediation is protected by Evidence Code section 1119, and the reach of that protection is broad — Cassel v. Superior Court (2011) 51 Cal.4th 113 shields even attorney-client discussions in preparation for mediation from later use. But confidentiality does not cure a false discovery verification made months earlier. The prior-claims problem gets solved in the written discovery, not in the mediation room.
Anticipate How the Defense Will Use the History
The defense has two theories, and they are different animals. The first is causation apportionment: this pain, this disc bulge, this limitation predates my client's tortious conduct, so pay for the delta and nothing more. That is a legitimate argument and you meet it with medicine. The second theory is character: your client is a serial claimant who sees a paycheck in every fender-bender. That argument is mostly inadmissible and you meet it with the rules.
Evidence Code section 1101, subdivision (a), bars evidence of a person's character or disposition to prove conduct on a specific occasion. A history of filing claims, offered to suggest your client is the litigious type who exaggerates, is exactly the propensity use the statute forbids. Prior claims can come in under section 1101, subdivision (b), only for a permitted non-character purpose — and even then section 352 requires the court to weigh probative value against the substantial danger of undue prejudice and confusing the issues. A stack of small prior claims has thin probative value on causation and heavy prejudicial pull. That is a motion in limine you can win, and both sides know it.
This split matters at mediation because it tells you which arguments deserve a real response and which deserve a citation. When the defense brief leans on the number of prior claims rather than the medical overlap, they are telling you they do not have the causation medicine. Say so in your caucus with the mediator.
Separate Genuine Apportionment From Noise
Where a prior claim involved the same body part, do the medical work that the defense expert is going to do, and do it first. Get the prior imaging, the prior treatment records, and any prior impairment rating. Line up the prior films against the current ones and have your treating physician or retained expert speak to the difference. A prior neck strain that resolved with six weeks of therapy and a current three-level fusion are not the same injury, and the imaging usually says so plainly.
Two CACI instructions carry the plaintiff's framing here, and you should be quoting them by number in your mediation brief. CACI 3927 tells the jury that a defendant is liable for aggravation of a preexisting condition, and that where the effects of the injury and the prior condition cannot be separated, the defendant is responsible for the entire condition. CACI 3928 — the unusually susceptible plaintiff, the eggshell rule — tells the jury that a plaintiff who was more prone to injury still recovers full damages for the harm actually caused. A prior injury that left your client more vulnerable is not a discount. Under the instruction, it is the opposite.
The reframe you want the mediator to carry is this: the prior claim does not reduce value, it explains why a moderate impact produced a serious injury in this particular person. Defense valuation models discount hard for "degenerative" and "preexisting"; the same evidentiary discipline that beats an overreaching hospital lien on a perfection defect — reading the records line by line rather than accepting the summary — is what separates real apportionment from a defense expert's boilerplate.
Build the Mediation Brief and the Caucus Script
Put the history in your own brief before the defense frames it in theirs. A short, unapologetic paragraph — here are the prior claims, here are the body parts, here is why the current injury is distinct or an aggravation — reads as confidence. Silence reads as concealment, and a mediator who feels handled will move your number in the wrong direction.
Prepare the client for the caucus explicitly. The defense may want a joint session precisely to watch your client react to the prior-claims file. Walk through each prior incident until the answers are calm, short, and accurate: what happened, what body part, how it resolved, and the truthful statement that this injury is different or worse. A client who gets defensive about a legitimate prior claim does more damage than the claim itself. The goal is a client who treats the history as unremarkable, because legally it mostly is.
Have the Numbers Ready
If a prior claim resolved for a documented amount, know it, and know the body part and the treatment it covered. When the defense argues overlap, a specific answer — the prior claim paid for eight physical-therapy visits to the lumbar spine, this claim is a cervical surgery — is worth more than any rhetorical framing. Case-valuation tooling is moving fast on the plaintiff side, and the same consolidation and analytics trend reshaping firm economics now lets smaller shops model apportionment scenarios that used to require a retained economist. Bring the delta to mediation as a number, not an adjective.
The Closing Read
A prior-claims history costs you money at mediation only when it arrives as a surprise or gets treated as shameful. Disclosed early, met with medicine on causation and with the character-evidence rules on everything else, and framed through aggravation and susceptibility, a history of prior claims stops being the defense's best exhibit and becomes just another fact you already priced in. The adjuster expected you to flinch. Don't.