The contents of your post do not raise any civil rights issues. Thus, I'm going to edit the practice area of your post to "Litigation" for better exposure.
Ms. Berjis is licensed to practice law in the State of California. The laws of your jurisdiction may differ and thus this answer is for informational and educational purposes only and is not to be considered as legal advice. Since all facts are not addressed in the question, this answer could change depending on other significant and important facts. This answer in no way constitutes an attorney-client relationship.
You generally cannot subpoena an expert simply because they're an expert (rather than being a witness to an event). You would instead *hire* them as an expert witness. It may be that they would be willing to volunteer, either because they're supportive of your cause or would like the exposure. But without more details, I see no way you can simply force this person to testify on your behalf.
Perhaps it might help if you gave us a hint as to what your case is about. But whatever the matter, you're likely to be better off in litigation if you retain your own attorney.
Licensed in Oregon. Advice provided is general legal information relevant to the facts provided. It is not intended as legal advice applicable to your specific situation. No attorney/client relationship is created unless and until we have met and entered into a written representation agreement. Contact me at 541-250-0542 to discuss your matter further. www.MaugerLaw.com
Its not the judge whoI wants to hear this author or even cares about what the author thinks---its you.
Writing a book does not obligate an author to you or anyone else and the author is under no obligation to testify for you. I guess you've figured that out by now,
Expert witnesses are PAID for their time--many charge several thousand dollars--more depending on how long they are needed, hotel, meals, transportation too.
You may consider asking the author how much he would require to be your expert witness. But again, he is under no obligation to help you.
NOT LEGAL ADVICE. FOR EDUCATION AND INFORMATION ONLY. Mr. Rafter is licensed to practice in the Commonwealth of Virginia and the US Federal Courts in Virginia. There is no implied or actual attorney-client relationship arising from this education exchange. You should speak with an attorney licensed in your state, to whom you have provided all the facts before you take steps that may impact your legal rights. Mr. Rafter is under no obligation to answer subsequent emails or phone calls related to this matter.
Mr. Mauger and Rafter have laid out the issue quite well. I concur with their analysis, but wanted to add that the Courts are _extremely_ reluctant to hear 'compelled' expert witness testimony. The general rule is that an opinion cannot be compelled from any witness. Facts, what you personally observed for instance, can be compelled but not your own thought processes about what you observed. There are all sorts of potential objections to this kind of testimony and Judges are loath to get down into those kind of fights.
If you try to compel an expert witness opinion, your potential expert witness will hire an attorney to keep him or her out of the case and you _could_ end up paying the bill for that expert's attorney and still end up without the expert's testimony. Further, a compelled witness -- unless their objections to testifying are entirely personal in nature -- is never going to be as persuasive and effective as a witness who wants to be there. If you have an expert, you will get what you pay for; sad to say but there it is.
If you are in the final stretches of the case, it might be possible to get your potential expert witness' information into evidence as _impeachment_ of the other side's own expert witness. This is _not_ substantive evidence, so you would not be able to surmount Summary Judgment or the like, but it might be enough to influence the trier of fact on your desired issue(s). The so-called Rieker line of cases has the substantive law on the use of learned treatises in Oregon practice. Reiker v. Kaiser Foundation Hosp., 194 Or. App. 709 (2004). If you can pull it off, it might even be possible to exclude the other side's expert witness in voir dire by the skilled use of a learned treatise by your book author. This is highly technical work and even many attorneys cannot pull it off except under perfect circumstances, and there are many cases where it simply not possible even with perfect advocacy, but it might be worth investigating. Compare ORE 803.18 with FRE 803.18 (there are substantive differences between Oregon evidence and Federal evidence practice on this point).