Earlier this month, outside the gates of the Centers for Disease Control and Prevention in Atlanta, parents angrily confronted government scientists.
They were passionate about one specific point of view -- that their kids had been poisoned by the mercury contained in the childhood vaccines they'd received, and now had autism.
These parents were frustrated by the mainstream media and mainstream medicine, which insists there is no evidence to support their theory. The parents believe that scientists allowed the poisoning to happen and were now covering up the truth.
In turn, many of these parents have gone and found a small group of scientists, doctors and researchers who also believe that the mercury in vaccines have caused autism.
And in this world, perhaps no set of names is more famous than Geier and Geier. Mark Geier is an M.D. with a Ph.D. in genetics. His research partner is his 26-year-old son, David Geier, who has no advanced degrees.
Together, the father and son duo argue in study after study that symptoms of autism are caused by mercury once widely used in vaccines.
When Mark Geier presented the research to the Institute of Medicine, perhaps America's highest medical authority, those who reviewed it declared the arguments so rife with "methodological limitations" that it was judged "uninterpretable." The link between vaccines and autism was found to be without foundation.
Though that was three years ago, the Geiers are still arguing the opposite view, and there is an audience still ready to hear that argument.
In a landmark vaccine trial being held in Washington, D.C., the Geiers serve as scientific consultants to a legal team representing nearly 5,000 families seeking damages.
Mark Geier has testified as an expert witness in more than 100 vaccine trails, though at times the court has not upheld his testimony. One court ruling in July 1993 called his testimony "intellectually dishonest," but Geier said he has "never been dishonest in any way, shape or form."
Although some of Geier's testimony has been deemed inadmissible in court, decades ago his work was firmly in the mainstream and he was considered something of a prodigy.
Mark Geier was featured in stories in Newsweek and The New York Times in October 1971 about a research team he was a part of at Johns Hopkins that completed the world's first successful gene-splicing procedure. At the time, he was only 23 years old.
He has a life outside the controversy. Over the years, he has prospered as a doctor running a profitable practice that offers genetic testing, such as amniocentesis for pregnant women. He is a tennis fanatic, as is his wife and his son David.
David Geier is often the spokesman for the two.
"They did studies, and they found harmful effects," David explained, referring to internal discussions at the CDC that started in the late '90s, which some activists construe as proof that the CDC was aware of a link between vaccines and neurological disorders. "But they're not going to tell the people, because no one would want to vaccinate their children. And we desperately don't want that to happen. So let's get rid of the mercury from the shots."