HALIFAX — There were "many red flags" warning that Howard Hyde was suffering from a condition known as excited delirium in the hours before he died in a Halifax-area jail cell, an expert on in-custody deaths testified Monday at an inquiry into Hyde's death.

Christine Hall, an emergency room doctor based in Vancouver, said the "constant and repetitive nature" of Hyde's behaviour on Nov. 22, 2007, was a strong clue he was suffering from the mysterious syndrome, which remains the subject of much debate and research within the medical community.

In Hyde's case, surveillance video recorded at the Central Nova Scotia Correctional Facility shows him pacing in his cell for hours on end in an unchanging, circular pattern.

"If you know what to look for, that behaviour is compelling. ... This is not a normal individual who is just bored," said Hall, a researcher with the Canadian Police Research Centre. "That should be one of many red flags that something is up."

Hall said this behaviour suggested Hyde was in a highly agitated or excited state -- a signal that he was suffering from excited delirium, a term that pathologists have been using since the 1980s.

"Often, staff are unaware that those symptoms on their own can be quite significant," said Hall, who wrote a report for the inquiry that recommended corrections staff should be trained to recognize that excited delirium is a form of "medical distress and not simply a behaviour problem."

The condition is usually marked by other signs, including incoherence, paranoia, extraordinary strength, profuse sweating, high blood pressure, an elevated heart rate and suddenly intense, violent behaviour, Hall said.

Corrections officers and police officers have testified that Hyde displayed some or all of these traits while in custody.

Hyde, a 45-year-old musician with a long history of mental illness and scrapes with the law, was arrested for assault on Nov. 21, 2007, after his spouse called police to complain he was abusive and off his medication for schizophrenia.

At the time, Hyde tried to escape police by climbing down the side of a low-rise building, dressed only in a pair of shorts despite sub-zero temperatures outside.

The inquiry, which started last June, has heard that Hyde was later Tasered up to five times and collapsed unconscious under a heap of officers as he tried to escape from the police station in downtown Halifax.

He was taken to hospital and released several hours later on the condition he receive psychiatric help once he appeared before a judge. But that never happened.

Instead, Hyde was taken to the provincial jail where he died after two intense scuffles with jail guards. A medical examiner later concluded that the cause of death was excited delirium.

Hall testified that she didn't believe the Tasering caused Hyde's death.

"There's no body of scientific evidence that the applications that he underwent caused an arrhythmia (abnormal heart rate) that resulted in his death some 30 hours later," she said. "It's extraordinarily unlikely that the Taser application was directly ... related to his death on the following day."

Hall said excited delirium remains a puzzling condition because researchers have yet to determine what causes some sufferers to suddenly die, while others recover without incident.

Typically, there is no anatomic cause of death -- as in Hyde's case -- and "we do not know what the preamble metabolically is," she said.

"Excited delirium as a title or a name has undergone incredible amounts of debate, seemingly without end," she said.