From CBC News...
The research in question took place over many years and involved inducing various degrees of pain in mice using methods such as dipping their tails in hot water or injecting them with mustard oil or vinegar. The faces of the mice were then photographed to understand how they express pain.
"No one likes putting animals in pain," said Mogil, who holds a Canada research chair in the genetics of pain. But he said in the case, the pain was necessary and scientifically justified.
....However, Leslie Norins, the publisher of the newsletter that led to the council's investigation, questioned Mogil's research methods.
"Mice were purposefully subjected to intense pain without anesthesia," said Norins. "In our reading of the national guidelines, this came very close to a violation.