The Inconsistencies of an Expert Witness


In my last post, I spoke about the experienced expert witness, Dr. Robert Brent. It turned out that Dr. Robert Brent had known Dr. Robert Staples for more than 30 years. You may recall that Robert Staples, the head of toxicology for DuPont, had conducted important benomyl studies in 1980 and 1982 for DuPont.

 

Dr. Brent had learned about Dr. Staples’s research on benomyl and had done two consultations for DuPont, including work on the 1980 Staples study.

 

He certainly had a lot of familiarity with the product, the research, the studies, and the potential impact of exposure to Benlate.

 

Dr. Brent disagreed with the findings of the 1980 Staples rat study and was well aware that the EPA had considered warning pregnant women about exposure to Benlate. He was also aware of the rebuttable presumption placed on DuPont, which had been lifted after the 1982 Staples study.

 

Despite our discovery to the contrary, Dr. Brent testified that the methodology of both Staples studies was the same. When I pushed him a little harder on the validity of the Staples studies, he said he could be persuaded to change his opinion about whether they were sound, solid studies that followed proper methodology.

 

While Dr. Brent believed the Hoogenboom study supported the 1982 Staples study, he admitted that most subsequent studies didn’t clearly determine whether there were no-effect levels and started out at the 62.5-milligram dose level.

 

He believed that a better study than the ones in existence would focus only on activity on the ninth day of gestation, because that was when microphthalmia could occur. The ninth day of gestation was the most sensitive day in rats for eye and lung formation, as well as for possible development of hydrocephalus, encephalocele (sometimes known as cranium bifidum, which is a neural tube defect) congenital heart disease, absent kidneys, and vertebral malformations, among other worrisome conditions. The most sensitive organ developing on the ninth day is the brain, and the eye is technically part of the brain.

 

Any study that tested benomyl on rats exposed between day four and seven would not result in microphthalmia. In order to see this malformation, the rat had to be exposed between days nine and eleven. The eyes don’t stop developing for quite some time, and neither does the brain, so vigilance thereafter is important, too.

 

What Dr. Brent was sure of was that if benomyl crossed the placenta in rats, then it crossed the placenta in humans. As long as a compound is in the mother’s blood and it gets to the placenta, it will get to the embryo or fetus.

 

Dr. Brent stated in his testimony that he had no doubt Johnny Castillo’s microphthalmia occurred within the proper time frame for a toxic agent to have produced it. He also had no doubt that the alleged exposure occurred during the critical period of Johnny’s eye development.

 

Although Dr. Brent said he wasn’t in a position to comment on whether Dr. Howard was unqualified to testify, he had no reason to believe he wasn’t. In fact, Dr. Brent thought Dr. Howard was qualified but wrong.

 

For this reason, he did his best to discredit Dr. Howard’s testimony and credentials, especially his in-vitro studies and his calculations regarding Donna’s exposure.

 

In the chemotherapeutic setting, however, the in-vitro tests determined exactly what Dr. Van Velzen had with exposure to benomyl, finding whether and when cell death occurs. The tests would confirm his findings. Dr. Brent also testified that he agreed that a genetic expert could not prove a genetic cause, and that Johnny and his family had undergone all the state-of-the-art tests available and the results had all come back negative.

 

Although Dr. Brent couldn’t say with a reasonable degree of medical certainty what caused Johnny’s microphthalmia, he couldn’t rule out an environmental factor such as benomyl exposure (which he considered a “very remote possibility”).

 

Despite his own testimony that he had no right to say within a reasonable degree of medical certainty that Johnny’s condition was recessive-inherited, X-linked recessive, or new-dominant recessive, and that every genetic test done on the Castillos came back negative, Dr. Brent still personally believed genetics was the most likely cause.

 

Given the facts, I had no idea what the basis of this opinion was. I could fathom only that it was meant to confuse the jury and dissuade them from the thought that the cause might have been benomyl.

 

I continue to recount Dr. Brent’s testimony, and my cross-examination, in my next post.

 

You’ll find a full narrative of the trial, the science behind the chemicals in question, the people involved and my own background, in my book, Blindsided, from which this blog post is adapted.

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