BRATTLEBORO -- Vermont's deputy chief medical examiner believes Nita Lowery died from "an acute hypoglycemic event" -- in other words, extremely low blood sugar.

But Dr. Elizabeth Bundock, despite performing an autopsy on the 83-year-old Brattleboro woman in April 2009, admits that the exact reason Lowery died -- at least, in her expert opinion -- remains a mystery.

"What I would like to know is the cause and I felt that I could not come to a certain decision about the cause of the hypoglycemia," Bundock testified Friday in Windham Superior Court Criminal Division.

Both pieces of information -- that Lowery died of hypoglycemia, and that the official manner of her death still is undetermined -- are critical to the murder trial of 39-year-old Jodi LaClaire, who is accused of giving Lowery a lethal dose of insulin and then stealing her money.

Prosecutors say LaClaire, at the time a nursing assistant, was responsible for Lowery at Brattleboro's Thompson House care home the night before the elderly woman was found unconscious.

Lowery -- who was not a diagnosed diabetic -- was rushed to Brattleboro Memorial Hospital the morning of March 23, 2009. She remained in a coma, was found to have suffered severe brain damage and died nine days later.

Years of investigation followed, and LaClaire, of Bennington, N.H., faces nine charges -- one count of second-degree murder, one count of abuse of a vulnerable adult and seven counts of financial exploitation of a vulnerable adult.

After three days of trial, however, there has been little testimony about what LaClaire -- who is a diabetic who uses injectable insulin -- did or did not do. Rather, testimony has focused mainly on how Lowery died.

Bundock was called to the stand because she performed an autopsy on Lowery the day after her death. As part of that procedure, she examined samples of Lowery's brain under a microscope in an effort to determine what had led to her coma.

She looked for signs of ischemia, or a lack of blood flow that might have been caused by a stroke.

"I did not believe ... that is what happened on March 23," Bundock said.

"It was more likely to be hypoglycemia," she added. "The pattern didn't fit with the pattern for lack of blood supply."

Bundock testified that she believes Lowery's heart and lungs did not contribute to her death. She also examined Lowery's liver and found no evidence of chronic alcohol abuse -- a behavior that had been asserted by LaClaire's defense attorneys earlier.

Also ruled out as causes of death were the pancreas and adrenal glands.

Under questioning from Vermont Assistant Attorney General Matthew Levine, Bundock said she could not rule out an insulin injection as a manner of death.

In fact, Levine pointedly asked her about a possible needle mark in Lowery's right forearm.

"Can you say anything about the timing of when that would have occurred?" he asked.

"It's not from the day of death, and that's about all I can say," Bundock replied.

She also affirmed Levine's speculation that it would be possible to inject someone with an insulin needle -- which is "very narrow gauge" -- and not leave a mark.

But overall, Bundock said she could not determine with any degree of certainty what had caused Lowery's blood sugar to plummet so unexpectedly.

"The manner of death flows from the cause," Bundock said. "If I cannot determine the cause of the hypoglycemia, then I cannot properly assign the manner of death."

Defense attorney Dan Sedon, near the beginning of what was to be a long cross-examination, declared that "medical research is extraordinarily deep" and even made reference to progress made since leeches were used for healing.

That was his jumping-off point for continuing to explore other possible explanations for Lowery's death. First up were tumors; Bundock testified that she had found a small, previously undiagnosed tumor in Lowery's lung during the autopsy.

Bundock had testified that she searched for -- and did not find during Lowery's autopsy -- a specific type of pancreatic tumor that can produce insulin.

Under Sedon's questioning, she acknowledged that "there are numerous types of tumors that can produce hypoglycemia" while adding that, "in the grand scheme of things, they're fairly uncommon."

"Isn't that the type of thing that can turn around and bite someone like you -- the uncommon thing?" Sedon asked.

Bundock recalled researching such tumors while investigating Lowery's case. That led Sedon to attempt to introduce a 1982 article on the topic from the Japanese Journal of Medicine, which touched off a lengthy debate and two bench conferences among Judge David Suntag and the four attorneys involved in the case.

The main question was whether a small tumor -- such as the one found in Lowery's lung -- could have caused her coma. But there was no firm answer as to whether that 1982 article should be considered reliable or relevant in this case.

Sedon moved on to other possible causes of a spontaneous drop in blood sugar including drugs, alcohol, certain types of organ failure and malnutrition. Bundock agreed that all were general possibilities and said she even consulted an endocrinologist in Lowery's case.

But she then circled back to her main conclusion, saying that interpreting why Lowery had become hypoglycemic "was becoming out of my field of expertise."

"Much of the time, I am dealing with manners of death that are not homicide," Bundock said. "When the question is homicide, I feel that I need to be certain or very close to certain."

She added this: "It was not proven with certainty that it was an exogenous (from outside the body) insulin injection, based on the data I had to review."

Sedon pressed on, questioning Bundock about the difficulty of distinguishing between hypoglycemia and a stroke caused by lack of blood flow.

She acknowledged that "they can be indistinguishable" but still asserted that "I felt what I saw could be consistent with what was believed to be a hypoglycemic event."

As far as the puncture wound Levine had asked about, Bundock told Sedon that it might well have been from hospital treatment.

Bundock's testimony consumed the afternoon on Friday. In the morning, there was a somewhat similar lack of certainty resulting from testimony by the day's only other witness -- Susan Shanoff, senior corporate fraud investigator for Peoples United Bank.

Peoples United owns Ocean Bank and Chittenden Bank, two of the institutions where LaClaire allegedly used Lowery's USAA card to withdraw thousands of dollars.

Testimony focused mostly on just two of those alleged instances -- March 31 and April 1, both at Ocean Bank on West Street in Keene, N.H.

Ultan Doyle, Vermont assistant attorney general, carefully tried to establish the origins of bank-surveillance photos from those transactions -- though he never introduced them into evidence or told jurors that they depicted LaClaire.

Nevertheless, defense attorney Richard Ammons asked numerous questions about the pictures' resolution, the camera system that records them, the way they had been sent to criminal investigators and whether they could have been tampered with.

"It can happen inadvertently?" Ammons asked.

"I personally have never seen it happen in all of the years I've been working," Shanoff replied.

She also said that, though her computer hard drive had been replaced at one point, she never lost access to the photos connected to the Lowery investigation.

But Shanoff also admitted that the system for retrieving those photos can be somewhat imprecise in terms of coordinating the time of the transaction and the time stamp on surveillance video.

"Overall, the time stamp is very accurate," Shanoff said. "It's within one or two minutes most of the time."

That did not satisfy Ammons.

"If a transaction takes place in two minutes, this question matters," he said.

The trial is to resume Monday morning and is scheduled through Sept. 27. Shanoff and Bundock were the prosecution's eighth and ninth witnesses.

Mike Faher can be reached at mfaher@reformer.com or 802-254-2311, ext. 275.