Our investigation led the BBC to Rader. They sent a patient to his Dominican Republic stem cell clinic with an undercover camera last year.
What you're about to see is what happened when that patient tried to back out.
"I want to go away and have another think about it and then come back," says undercover reporter Linda Oatley on the undercover video.
"Don't let her do that. Don't let her do that," says Rader. "Because there's no more to think about."
"I'm incredibly nervous," says Oatley.
Nervous or not, Rader pressures Oatley, a multiple sclerosis patient, to begin treatment immediately.
What Rader doesn't know is that Oatley is wearing a hidden camera and secretly filming her visit to Rader's clinic in the Dominican Republic for the BBC.
"Let's just get started," says Rader on the video. "He can go get the money later. Let's just get started. We're going to start right now."
Stem cells are cell factories able to turn themselves into almost any cell in the body, such as a heart, liver or nerve cell.
While the promise is there, proven treatments are still years away. But that doesn't stop Rader from making some pretty incredible claims on his website.
"The list of diseases that fetal stem cells have an impact on is enormous," says Rader in an online promotional video. "It includes things like Parkinson's, multiple sclerosis."
Oatley was diagnosed with multiple sclerosis 10 years ago.
"And then one day I tripped, I just caught my right toe -- and I looked around, and there was nothing there for me to trip on, and I knew, I just knew."
The British Broadcasting Company asked Oatley to help investigate Rader's claims. She would be passing herself off as a paying customer, and would be expected to hand over $30,000.
"Number one, we see with all our MS patients that they do get better," said Rader on tape. "We have patients who are walking who were in wheelchairs. I'm the only one in the world basically doing this."
Dr. Evan Snyder is a renowned stem cell scientist.
"Oh, this makes me astoundingly angry," said Snyder. "Not only is he harming patients, but he's also harming the field."
Snyder has offered to test and examine Rader's cells. Rader declined.
"I think he won't let me look at those cells because he knows that he'll be revealed to be the sham that I believe he is," said Snyder.
Eyewitness News went to Rader's Malibu office for a response.
"We're saving lives, and I'm the only one in the world doing this. I'm the only one in the whole world," said Rader. "So the doctors are against me, the pharmaceutical companies are against me, the religious right is against me."
Rader derides Snyder as a so-called "mouse researcher," and says that undercover video is slanted.
"So it was very prejudicial," said Rader. "But it's not important to Bill Rader, because I'm a good boy."
"Let's just get started," says Rader on the BBC video. "We're going to start right now."
"That's horrific, actually," said Snyder. "No physician ever, ever tries to pressure a patient into receiving an experimental therapy."
"I was pressuring them because I believed it was a real patient," said Rader in Malibu. "You asked me if I would do that again, I probably would under the same circumstances."
"We in my field call those guys scam artists, snake oil salesmen, slick, used car salesmen," said Snyder.
After insisting she needs more time to think, Oatley goes back to her hotel.
"This guy plays on the vulnerability of people that are disabled and who have got money and are prepared to travel, and they come for the 'magic cure,' and it doesn't exist," says Oatley on video after her meeting with Rader. "It just doesn't exist."
Rader provided Eyewitness News with video, claiming it shows another MS patient, Kevin Paginton, who was also treated at his Dominican Republic clinic.
Paginton told Eyewitness News by phone from Bath, England, that just seven days after Rader's treatment, he was out of his wheelchair and walking. Eyewitness News was not able to independently verify the circumstances surrounding the production of the video, nor his medical condition.
The California Medical Board can't do much because Rader's clinic is out of the country, but the board did issue him a citation in December 2009 for disseminating "false and misleading advertisements through various Internet websites." Rader was fined $1,500. He is appealing.