Charges have been withdrawn against an Ontario woman who spent 13 years in jail after being convicted of killing her toddler — in part because of evidence from now-disgraced pathologist Dr. Charles Smith.

Tammy Marquardt was convicted of second-degree murder in the death of her two-year-old son Kenneth Wynne in 1995.

But the conviction was based on evidence from pathologist Charles Smith, who was recently stripped of his medical licence for professional misconduct and incompetence. He testified at Marquardt's trial that Kenneth was strangled or suffocated, when the toddler had actually died of an epileptic seizure.

Earlier this year, the Court of Appeal for Ontario quashed Marquardt's second-degree murder conviction, calling her a victim of a miscarriage of justice and ordering a new trial.

Marquardt said nothing could be done to compensate for what Smith has done.

"I don't think that anything could vindicate," Marquardt told reporters outside an Oshawa court. "He has to live in his own personal hell and so there's nothing that really that I or anyone else could do.

"I would ask him what he thought he was doing and who he thought he was and why, why did he do it? What possessed you to play God?"

Coroner's review

An Ontario coroner's inquiry reviewed 45 child autopsies in which Smith had concluded the cause of death was either homicide or criminally suspicious.

The coroner's review found that Smith made questionable conclusions of foul play in 20 of the cases — 13 of which had resulted in criminal convictions. After the review's findings were made public in April 2007, Ontario's government ordered a public inquiry into the doctor's practices.

That inquiry, led by Justice Stephen Goudge and concluding in October 2008, found that Smith "actively misled" his superiors, "made false and misleading statements" in court and exaggerated his expertise in trials.