Many, many cases that are going to court involve an expert on one topic or another. I would bet that in cases involving pro se litigants on one side against an attorney on the other, experts are used even more often.
Because usually the only way to battle an expert is with an expert.
In other words, if you are representing yourself and facing an expert on the other side then you are more likely to face a Motion for Summary Judgment which you will have to have an expert to provide reports to counter.
However, even more important than that is the fact that at some point you are going to face that expert either in a deposition or live on the witness stand.
Many people make the fatal (to their case) of thinking they can go headto head with an expert because they have read a few articles on the internet but the simple fact is taking an expert on head to head is usually a guaranteed loss.
However, there are ways to beat an expert.
First, in your discovery ask for every document, article, periodical, learned treatise, book, etc. that he used to form his opinion or that he relies on in the normal course and scope of his practice. If you go to his office to do a deposition be sure and make a note of all the books that are on his shelves and, if it is a video deposition, ask the videographer to film them.
If it is a deposition, ask him which books he has that he does not think are authoritative.
Next, examine a copy of all of those materials to see what they say about his opinion as well as where they disagree. Be sure and look for the sources that are cited in those books as well.Many times the sources that he uses or considers authoritative will also cite other sources that disagree with them.
The expert's main purpose when he comes into court is to provide testimony for the person that hired him. However, underlying this intent is the fear that he will be caught in a mistake or that his opinion can be proven wrong. For a litigant to win against an expert they don't have to prove him wrong, they just need the judge or jury to doubt that what he said is correct.
The litigant appearing pro per or pro se can also look on the internet for copies of depositions of this wirness which have been taken in other cases. On more than one occasion I was able to locate old depositions where he had taken the exact opposite position than he was now taking in my case. That is devastating to his credibility.
Finally, never start arguing with the expert about his area of expertise. You will never know as much about their topic as someone who works in that area every day. What you can do is look for areas that he didn't consider. As an example, on a case I once had the expert stated that the soil under a house hadn't been compacted enough to support the weight of the house built on top of it. Rather than arguing about it, I attacked the fact that he had formed that opinion without testing the soil under the house or being present when it was compacted and therefore was rendering an opinion on less than complete information and the whole thing could have been solved if he had drilled under the house and taken a sample.
An expert who testifies at trials does not want to get the reputation of being easy to beat or of doing incomplete work. The more time a litigant spends talking about what the expert did wrong the less time the jury hears about what he did right.