There are experts and then there are experts. Court cases can end up being Dueling Experts, with each side's experts testifying for what they're being paid (they rarely do it gratis) for by each side. Once every year the attorneys I work with get a big fat book of the names, addresses, phone, fax & e-mail of experts, listed by category. Some experts don't practice in their field anymore--they just testify for their fees.
One of the best expert witness I've seen is Dr. Park Dietz, who convinced a jury that Jeffrey Dahmer was sane--he just liked to kill and eat people.