By James McIntosh

A new study reveals that a group of physicians have testified for the tobacco industry against patients dying of cancer on multiple occasions, repeatedly stating that their smoking habits did not cause cancer.

According to the study conducted by a researcher from Stanford University, a pool of six experts would testify as expert witnesses that a combination of environmental factors such as the use of mouthwash or the consumption of salted fish were more likely to have caused a patient's head and neck cancers than heavy smoking.

"I was shocked by the degree to which these physicians were willing to testify, in my opinion in an unscientific way, to deny a dying plaintiff - suffering the aftermath of a lifetime of smoking - of a fair trial," says study author Dr. Robert Jackler, professor and chair of otolaryngology-head and neck surgery.

For the study, Dr. Jackler analyzed cases occurring between 2009 and 2014 in which patients were suing tobacco companies for damages. The patients were all long-term, heavy smokers with cancer in sites such as the larynx, mouth and esophagus.

In these lawsuits, the matter being debated was whether or not smoking caused each plaintiff's cancer. Dr. Jackler consulted expert witness depositions and trial testimonies for each case before reviewing scientific literature to see whether the expert witnesses were supported by evidence.

"The study found they used scientifically invalid methods to support their testimony," Dr. Jackler states.

Tobacco companies R.J. Reynolds, Philip Morris and Lorillard paid the six board-certified otolaryngologists - physicians specializing in diseases of the ear, nose, throat and related structures - to testify on behalf of the tobacco industry in over 50 cases.

The testimony provided by these expert witnesses was found to be remarkably similar across different cases, the study reports, and part of a cohesive strategy to dissuade the jury from ruling against smoking:

"By highlighting an exhaustive list of potential risk factors, such as alcohol, diesel fumes, machinery fluid, salted fish, reflux of stomach acid, mouthwash and even urban living, they created doubt in the minds of the jurors as to the role of smoking in the plaintiff's cancer."

Dr. Jackler points out that this tactical narrative is greatly flawed in that billions of nonsmokers are regularly exposed to these environmental factors.

"Were these causative factors for head and neck cancer, with even a minute fraction of the potency of tobacco, the rate of head and neck cancer among nonsmokers would be much greater than what has been observed," he argues.

The study suggests that the tobacco companies were willing to go to great lengths to obtain strong testimonies. One physician states that tobacco company lawyers wrote an opinion for her that she then had to approve while another refused to acknowledge reports from the Surgeon General as authoritative sources.

Providing a testimony for the tobacco companies was also found to be a lucrative move. One of the physicians reported they were paid $100,000 to testify in one single case.

In cases concerned with whether or not smoking caused a plaintiff's cancer, the legal standard is a probability of greater than 50%. Dr. Jackler says current scientific literature holds that tobacco directly contributes to head and neck cancer at a greater than 50% likelihood.

He dismisses the repeatedly expressed opinion of the six experts in the study that tobacco did not cause the plaintiffs' cancer as "not credible."

"The tobacco industry identifies the best experts that money can buy, trains them in their well-honed narrative to manufacture doubt in the minds of the jury and makes use of them over and over in case after case," the study concludes.

Dr. Jackler's study was supported by Stanford University School of Medicine's Department of Otolaryngology-Head and Neck Surgery.

In 2012, tobacco companies - including R.J. Reynolds, Philip Morris and Lorillard - were ordered by a judge to inform in product warnings that they deceived consumers regarding the risks of smoking and deliberately manufactured cigarettes to make them more addictive.