Damage cases involving a plaintiff with medical issues that pre dated the injury are challenging. I believe one important rule involves openess and honesty about the facts. An essential part of persuasion is complete authenticity, sincerity and the trustworthiness of the lawyer. I believe these cases require full disclosure of the pre-existing situation during voir dire, opening statement and trial. The opening statement should continue the same approach of full disclosure. Consider using PowerPoint that summarizes the jury instruction on the issue of pre-existing injuries. Framing in these cases is of vital importance. Some of the slogans that come to my mind involved:
(1) the greater the risk, the greater the duty of care – liability
(2) it’s not what you take away, it’s what the person is left with the accounts
(3) a chain is only as strong as its weakest link
4. There are a number of standard arguments dealing with pre-existing conditions and damages. Craig Spangenberg was a great teacher and plaintiff trial advocate. He developed the “egg shell victim” argument. It is based on the law the defendant is responsible for harm to your victim as you find them, regardless of whether they were more vulnerable or easily injured than “average” people. The argument went as follows, as recounted by James W. McElhaney in the American Bar Association Journal:
“We come to the subject of damages, and it’s a difficult area of decision. Oh, I wish this were a simpler case like a farmer driving his pickup truck on a country road when someone speeds through the stop sign, runs into his truck and turns it over.
“The farmer’s not hurt, but his truck is. One side’s all dented in, the windshield is broken out and a fender is torn off. And if you as a jury were asked, ‘What’s fair compensation for what the driver of the car did to the farmer’s truck?’ you wouldn’t have any problem with that.
“You’d give him the kind of truck he had. You wouldn’t give him a new truck, because he didn’t have one. But he shouldn’t have to drive a truck that’s all bent up and missing a windshield, because he didn’t have that, either. So fair compensation–just compensation–would be to pay him what it would cost to fix the truck he has. And I’m sure that my friend for the defense would accept that.
“Well, now suppose that the plaintiff is a poultry farmer and he has the back of his truck filled with eggs, three-hundred dozen grade A eggs, all carefully boxed and crated. And the defendant speeds through the stop sign, just like he did in this case. As a result you have three-hundred dozen grade A whites and yolks running all over the pavement. “What is fair compensation? Those are his eggs. They were marketable. His property has been taken away. His income has been taken away.
“What is fair compensation? Ninety-six cents a dozen retail?
“No. He wasn’t going to sell them retail. He was going to sell them wholesale, and the wholesale price reported in the newspaper was forty-seven cents a dozen. So he’s entitled to forty-seven cents times three hundred. One hundred and forty-one dollars. Now, in this situation, wouldn’t you think the defense lawyer had taken leave of his senses if he told you, ‘Don’t you pay him a hundred and forty-one dollars for those eggs! Why, if they’d been golf balls, not one would be broken.’
“I’m not telling you Mike Wilson was an egg, but he was like an egg. He was fragile. But he was still useful and marketable. He was able to sell what strength he had in the marketplace of labor.
“But he certainly was not a golf ball, and when the defendant sped through the stop sign and hit Mike Wilson, he did not bounce.
“And fair compensation is to restore the loss that has actually been inflicted on the actual man or woman. Just like when you break an actual egg, fair compensation is paying the actual value.”
This is just one example of dealing with pre existing injuries. See standard jury instructions and case law to furlther guide your approach.