Legal Question in Personal Injury in California

Doctors and expert witnesses, like lawyers, don't work for free. Mold cases are a longshot, so good luck with that.

You won't find any experts that work on lien basis. All experts, doctor or otherwise, require agreed upon payment for services, in advance. It is unethical for them to take liens. Doing so would destroy their credibility in court anyway.

You will need to pay the expert witness or have a lawyer that will front the money for the expert if the lawyer feels you have a strong case. There are litigation funding companies that will lend you money for litigation costs but only if the lawyer certifies that you have a winnable case. Those cases are hard to win. An expert who works on a lien, which are not generally around, would not be worth having since he or she would have an interest on your winning the case and not much credibility with the jury.

You have gotten correct answers so far. The key point is that experts are all suspect from the outset because they are being paid by the party employing them to give the opinion. An expert who not only is paid to say what you want, but also only gets paid if you win, would be utterly ignored by a jury. I would also add that you are highly unlikely to find ANY expert who will back up a mold case these days. So-called "toxic mold" has been proved to be a figment of litigators' imaginations and all the toxic mold studies have been debunked. There is no qualified expert today who will testify that any mold is anything more than an allergen. That is why insurance companies won't cover "mold poisoning." It's a myth.