Can a WSIAT Decision Be Reopened Decades Later in Ontario?

Can a WSIAT Decision Ever Be Reopened in Ontario?

Yes — but the bar is deliberately very high. The Workplace Safety and Insurance Appeals Tribunal (WSIAT) has the discretion to reopen a final decision, but only in limited circumstances. Simply disagreeing with the outcome or wanting to re-argue the same facts is not enough. Recognized grounds include a fundamental error of law or process that would likely change the result, or substantial new evidence that was not available at the original hearing and would likely have produced a different decision.

In Decision No. 1101/02R, 2026 ONWSIAT 903 (CanLII), a Vice-Chair granted a reconsideration of a 2002 ruling that had denied a deceased worker’s estate benefits related to an occupational disease claim. The case illustrates exactly what it takes to clear that high threshold — and what won’t get you there.

What Is the ‘Substantial New Evidence’ Test at WSIAT?

Substantial new evidence means evidence that was genuinely unavailable at the time of the original hearing and that would likely have changed the outcome. The Tribunal has described this standard as requiring evidence that is so logically persuasive it could be called practically conclusive on the disputed point — not just helpful or supportive, but powerful enough to outweigh everything that led to the original decision.

In this case, the worker’s estate relied on two detailed medical reports from an occupational medicine specialist, supported by multiple studies and case reports published after the original 2002 decision. Those materials addressed the evolving scientific understanding of the link between occupational silica exposure and connective tissue diseases. The Vice-Chair found that this body of evidence crossed the threshold.

What Was the Original Dispute About?

The original 2002 decision accepted that the worker had developed a serious autoimmune muscle disease (dermatomyositis) that contributed to fatal respiratory failure. What it could not establish at the time was a probable causal link between the worker’s occupational silica exposure as a miner (and his accepted silicosis) and that autoimmune disease. The medical opinions available in 2002 acknowledged a possible connection but fell short of the balance-of-probabilities standard required for compensation.

Critically, the original Vice-Chair left the door open — noting that if new scientific evidence emerged in the future, the estate could seek reconsideration. That invitation, made over two decades ago, is what the estate ultimately acted on.

Does a Long Delay Kill a Reconsideration Request?

Not necessarily, when the delay is caused by the pace of scientific development rather than inaction by the applicant. WSIAT’s own practice guidelines encourage reconsideration requests within six months of a decision, and a longer delay can count against an applicant. However, the Vice-Chair here gave the delay very little weight for three reasons: the very nature of the reconsideration ground (new science) takes time to emerge; the disputed question involved causation between established, undisputed facts; and there was no concern about evidence going stale. Based on affidavits from the worker’s daughter (the estate trustee) and an OHCOW coordinator, the Vice-Chair also found the estate was diligent in bringing the request within a reasonable time after the new evidence was published.

This is an important nuance for estates or surviving family members who may be sitting on older WSIAT decisions involving occupational disease claims where the science has moved on.

What Evidence Will Not Qualify as ‘Substantial New Evidence’?

Evidence that directly responds to or critiques the original decision is treated as reply evidence and is excluded. The Vice-Chair in this case specifically set aside portions of the medical reports that were written in response to the 2002 ruling’s reasoning, rather than reporting independent scientific developments. That material did not count toward meeting the reconsideration threshold.

This distinction matters practically: if you commission a medical opinion whose primary purpose is to argue that the original decision got it wrong, that opinion is unlikely to open the door to reconsideration on its own. The qualifying evidence must represent a genuine advance in knowledge, not a rebuttal.

What Happens After a Reconsideration Is Granted?

Granting the reconsideration request does not mean the estate wins the underlying claim. It means a new hearing on the merits will be scheduled. In this case, the Vice-Chair ordered that an independent Tribunal Medical Assessor’s opinion be obtained before any decision on the merits is issued, and that the estate’s representative will have the opportunity to address what questions are put to that assessor. The Vice-Chair who decided the reconsideration remains seized of the matter.

For workers and estates navigating the WSIAT process, our Ontario employment law lawyers can help assess whether new medical or scientific developments might support a reconsideration request in an older claim.

Does This Decision Apply to Other Occupational Disease Claims?

The principles confirmed here — the substantial new evidence test, the treatment of reply evidence, and the approach to delay — apply broadly to WSIAT reconsideration requests, not just silica or autoimmune disease cases. Any occupational disease claim where the science has evolved since a final decision could potentially be revisited, provided the new evidence is genuinely powerful enough to meet the threshold.

If you are in the Hamilton area, see our Hamilton employment law page for local contact information.

Questions and Records to Discuss with a Lawyer

• What was the date of the original WSIAT decision, and what specific finding was made about causation or entitlement?
• Has peer-reviewed research been published since the original hearing that addresses the medical or scientific question that was decided against the worker?
• Are there medical opinions already on file, and do they respond to the original decision’s reasoning or report independent scientific developments?
• What steps has the estate or worker taken since learning of new evidence, and when did that evidence become available?
• Are there affidavit materials that could demonstrate diligence in bringing the reconsideration request?

If you have questions about a WSIAT decision or an occupational disease claim, the team at UL Lawyers is available to discuss your circumstances. Reach out through our contact page to start a conversation.

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This article is automated commentary on a public court decision and is for general information only — not legal advice. Decisions rely on facts unique to each case. If you are affected by a similar issue, contact a lawyer for advice specific to your situation.