Almost by definition, you can not have a "volunteer expert witness." In order to be credible as an expert witness, the guy has got to be paid. The fact that you've paid him establishes his credibility. After all, any truly credible expert wouldn't work for free.
Expert witness work is a skill in and of itself. He not only has to be well-qualified in the subject at hand, he not only has to know his stuff. He has to know how to present his evidence in such a way that the judge (who, while smart enough to have made it through law school and ascended to a judgeship, is a lawyer -- not a knife expert) and the jury (again, not a group of knife experts and probably not a highly-educated or overly sophisticated group either) can under it and believe it. And yet the expert has to do this within the rules of evidence. He has to know how to work with your lawyer to give testimony that supports your case, does not give any support to your opponent's case, leaves no room for appeal, and fits squarely within the rules of evidence. Finally, he has to know how to withstand a brutal attack by the other side's lawyer.
He has to be about 75% expert in his field, 25% lawyer, and 25% skilled debator. Wait a minute! That's 125%! And that's right. That's why these folks are special.
Each time the expert witness takes the stand, he's putting it all on the line. If the opposition lawyer tears his testimony to shreads and disgraces him, or if his testimony ends up helping the opposition win the case, or if his testimony isn't enough to win the case for you, of if it's subsequently thrown out on appeal, etc., then he's gonna have a hard time finding work as an expert witness again. (The legal community is not that large and no lawyer hires an expert witness without looking into his background a bit.)
That's why these people have to be paid. It's not simple work and the stakes for the expert personally are just way to high.
You don't just show up for court on time wearing a decent suit and answer a few simple questions by spouting technical terms. A good expert witness spends many hours preparing. He knows not only the technical issues throughly, but the legal issues on both sides of the case as well. He's researched the technical aspects of the situation and the legal aspects too. He's spent hours racking his brain to think of all the possible questions he might be asked. Then, like a major-league batter stepping up to the plate at the bottom of the ninth with two outs, bases loaded, and his team down three runs: he puts it all on the line. Drive that ball out of the park and you're a hero; there'll be a sheet cake and everything. Oh, and your agent will negotiate a nice little raise and some lucrative endorsment deals for you too. But, strike out and you may find yourself traded to a backwater team for a minor-leaguer and half a case of vintage wine. Very few credible, professional expert witnesses will volunteer to take that sort of chance for free.
I have a friend who is a professional expert witness. He's considered one of the leading experts on death by electrocution. He's worked many product liability cases, a lot of negligence cases, and quite a few murders too. He often works full-time for a month or two on a single case. Only a few hours of that will be spent in court.
. He has great expierence with this type of stuff.
