A veteran pathologist and his young protegé looked at the neurological specimens and both concluded that chiropractic neck manipulation likely caused the stroke that killed Lana Dale Lewis.

Almost six years later, the rookie, now a prominent pathologist whose services are in demand around the world, no longer believes the neck adjustment led to the death of the 45-year-old mother of three.

"We were wrong," Michael Pollanen told a coroner's inquest yesterday. "In retrospect, our conclusions were erroneous."

However, he was using the royal we. His mentor, John Deck, strongly disagrees.

During eight days of aggressive questioning and cross-examination, Dr. Deck, now retired, told the inquest that he was 90-per-cent certain that his original finding in 1996 was correct.

Dr. Pollanen -- who came to the hearing from East Timor where he was performing autopsies for the United Nations on possible torture victims -- said he can say with a "reasonable degree of medical certainty" that Ms. Lewis died of natural causes.

The inquest is looking into whether there is a link between the stroke that killed Ms. Lewis and neck manipulation performed by a Toronto chiropractor who was treating her for migraine headaches. Her neck was adjusted on Aug. 26, 1996. She died Sept. 12.

Dr. Pollanen said his original conclusion was based on an incomplete examination. Some key cuttings of the left vertebral artery in the neck and just inside the skull were not examined until last year. These are the areas where injury would be found if chiropractic manipulation caused Ms. Lewis's stroke, the coroner's jury has heard.

Dr. Deck testified that he was not aware that Dr. Pollanen had not examined the slides when he co-signed a report in April of 1997 that listed neck manipulation as the probable cause of the stroke.

Dr. Pollanen conceded mistakes were made in the original investigation of the cause of death and that some were his. "If I had to do the case over, there are several things I'd do differently," he said during questioning by coroner's counsel Tom Schneider. Both men were testy during several exchanges.

Dr. Pollanen did not receive his medical degree until 1999, but he had a doctorate in neuropathology when he worked as a consultant with the coroner's office in Toronto under Dr. Deck's supervision in 1996. He had performed nearly 1,000 autopsies by that time.

Dr. Pollanen recanted his original conclusion after examining 507 new slides of tissue, bone and arteries -- the most of any autopsy he's conducted. Although the original slides could not be found, nothing he observed in the new slides supported a link to chiropractic treatment, he said.

He now concludes that Ms. Lewis's stroke was due to atherosclerosis, a progressive thickening of the wall in the left vertebral artery as a result of fatty deposits. High blood pressure caused the damage to the artery, he said.

Two vertebral arteries run along the back of the neck and into the skull. The new examination revealed that the left vessel was completely clogged while the damage in the right one was less severe.

His hypothesis is that the blood clot started in the head and worked its way down into the neck, a process called "retrograde extension."

He pointed to a 1973 study in a medical journal that found a clot had travelled from the skull into the neck area in 13.5 per cent of the 44 people examined.

Dr. Deck testified that the deadly clot formed when the neck was twisted by the chiropractor and it made its way into the head.

Mr. Schneider took Dr. Pollanen to task for not reviewing literature on neck manipulations and strokes before concluding they were linked.