"A whole set of issues come up. The other side may be trying to smear you," says Loeb University Professor Walter Gilbert, who has testified in two patent cases this year. "It's not a hobby. It's a serious business."

Mansfield recalls asking a colleague at Harvard Law School for advice before testifying in Colorado.

"I consulted a friend...who said, 'Don't do it. They'll cut you to pieces,'" Mansfield says. "I said confidently, 'What can they do to hurt me? They can only make a fool of me.' That certainly was bornout."

"You have these dreams of glory that you'll take an experienced lawyer and turn him into a bundle of confusion. I didn't succeed in that at all," Mansfield says. "I left a couple of quarts of blood on the witness stand."

Expert Witnesses

Warren Professor of American Legal History Morton J. Horwitz says the Supreme Court has recently put limits on expert witnesses and the topics on which they may testify.

In a 1993 case, Daubert v. Merrill Dow Pharmaceuticals, a woman who had a child with a birth defect sued the drug company, claiming the drug had caused the defect.

"The only witness that the plaintiff had was a doctor who had gone on a crusade saying the drug caused defects. There was no conventional scientific study," Horwitz says. "The question was, 'Can anybody with professional credentials be an expert witness or do you need to have studies?'"

"The Supreme Court leaned very strongly toward keeping 'quack' witnesses off the stand," he says.

Horwitz says expert witnesses have become indispensable in tort and personal injury cases. But these expert witnesses are very expensive.

"To get expert witnesses, you have to pay them, put them up in fancy hotels, pay for transportation," Horwitz says. "The expert witness requirement is sort of a wealth bar to suing."

Horwitz also points out that in many cases both sides have expert witness, each with experience and credentials.

"On all of these questions, the experts testify in different ways," Horwitz says. "It justifiably creates a degree of cynicism of whether [the witness] is testifying for the person who pays the piper or is giving a dispassionate, disinterested professional judgment."

In the only case in which he has testified, Horowitz says he definitely felt pressure to say what the attorneys who hired him wanted. Horwitz testified as an historian in a case about who owns the land under the Atlantic Ocean.

"They didn't care if I was an historian," he says. "I felt that they constantly wanted [me] to testify beyond what I could conscientiously testify to as an historian. I felt a real tension."