DISSENTING OPINION BY
Judge FRIEDMAN.In this issue of first impression, the majority determines that a claimant who suffers from mental impairment may not petition for review of a Workers’ Compensation Compromise and Release (C & R) Agreement on grounds that-she was incapable of understanding its ramifications because the doctrine of collateral estoppel forecloses this relief to any such-claimant as a matter of law by virtue of the very finding she seeks to have reviewed. I believe that such a result is both absurd and unjust; therefore, I must respectfully dissent.
In this case, Marcella Stiles (Claimant), while employed by the Department of Public Welfare (Employer), sustained a work-related injury described as “post-concussion syndrome.” After Claimant went through various periods of total and partial disability, her then attorney filed a petition on Claimant’s behalf, seeking approval of a C & R Agreement pursuant to section 449 of the Workers’ Compensation Act.1 At a hearing on the matter, Claimant testified that she accepted the terms of the C & R Agreement and had been fairly represented-by her attorney. Crediting this testimony, WCJ Francis J. Desimone (WCJ Desimone) found that Claimant understood the full legal significance of the C & R Agreement which she signed,2 (WCJ Desi-mone’s Findings of Fact, No. 4), and approved the C & R Agreement.
Claimant subsequently filed a petition (Petition) to reinstate her disability benefits, alleging that, “[a]t the time [Claimant] entered into her Compromise and Release, she was suffering from severe .psychological, psychiatric and physical injuries which gave her post-traumatic stress syndrome and [she] did not understand the economic value of her claim. The agreement was totally inadequate under the circumstances and should be set aside and benefits reinstated.” (R.R. at 18.)
Claimant’s Petition was assigned to WCJ Charles A. Getty (WCJ Getty), who initially continued the matter so that Claimant’s counsel could schedule the deposition of Claimant’s treating psychologist. However, shortly thereafter, Employer’s counsel moved to dismiss Claimant’s Petition; Employer contended that the issue of whether Claimant understood the import of the C & R Agreement already had been decided by WCJ Desimone, and, because Claimant did not appeal from that decision, the doctrine of collateral estoppel now precluded Claimant from revisiting the question. After considering the parties’ positions,3 WCJ Getty agreed with Em*1127ployer and dismissed Claimant’s petition. The WCAB affirmed, and now the majority also affirms. I cannot agree with such a result.
As the majority correctly states, Claimant’s Petition actually is in the nature of a petition to set aside the C & R Agreement pursuant to section 413(a) of the Act, 77 P.S. § 771, which gives the WCJ authority to set aside an agreement of the parties “if it be proved that such ... agreement was in any material respect incorrect.” 77 P.S. § 771 (emphasis added). The majority contends that it is with section 413(a) in mind that it considers whether Claimant’s Petition was properly dismissed based on collateral estoppel, (majority op. at 8); yet, the majority invokes the doctrine of collateral estoppel to deny Claimant the opportunity to prove that she was mentally incapable of understanding the C & R Agreement and bases the decision solely on WCJ Desimone’s finding that Claimant did understand that Agreement. By so holding, I believe that the majority eliminates the possibility of relief which the legislature intended to provide through this section of the Act. Indeed, because a claimant seeking relief under section 413(a) of the Act, 77 P.S. § 771(a), is required to prove the existence of a material mistake of fact or law, it makes no sense to hold that a claimant is prevented from offering such proof by the very “fact” she has challenged.4 Because such reasoning leads only to absurd results,5 I cannot accept the majority’s analysis in this case.
Moreover, I believe that the doctrine of collateral estoppel cannot be applied in this case because the issue before WCJ Desi-mone in the C & R Agreement approval proceeding under section 449 of the Act, 77 P.S. § 1000.5, is not identical to the issue before WCJ Getty in the proceeding to set aside that C & R Agreement under section 413(a) of the Act, 77 P.S. § 771.6
*1128■ In order to have effect, a C & R agreement must be approved by a WCJ after the WCJ considers the proposed agreement in open hearing. Before deciding whether to approve any C & R agreement, the WCJ must first determine that the claimant understands the full legal significance of that agreement. 77 P.S. § 1000.5(b). Thus, in the proceeding to approve the C <& R Agreement here, WCJ Desimone had to determine, based on the evidence presented at the C & R Approval hearing, whether Claimant understood the legal significance of the Agreement ‘ she signed. I believe this is very different than determining whether Claimant is mentally competent to attain such understanding.
Indeed, I take issue with the majority’s statement that “[ijnherent in that responsibility is a requirement that the WCJ determine that the claimant is mentally competent ...” (Majority op. at 1124.) To the contrary, the WCJ lacks the medical training that would qualify him to make this specific determination. See Southeastern Pennsylvania Transportation Authority v. Workers’ Compensation Appeal Board (Herder), 765 A.2d 414 (Pa.Cmwlth.2000), appeal denied, 566 Pa. 654, 781 A.2d 151 (2001) (stating that, while the claimant was qualified to testify concerning the decedent’s emotions prior to death, a medical expert is required to testify regarding the decedent’s alleged depression). Here, WCJ Desimone did not consider expert medical testimony on the subject of Claimant’s mental competence; rather, WCJ Desimone heard Claimant state that she understood the terms of the C & R Agreement, and the WCJ made his finding based upon that statement. Thus, in the C & R Agreement approval proceeding, WCJ De-simone simply made a credibility determination; that determination was in no way an expression of the WCJ’s expert medical opinion. WCJ Desimone’s ruling was on Claimant’s veracity, and Claimant’s mental competence was not an issue actually litigated at the hearing before WCJ Desi-mone. Based on this same reasoning, Claimant’s mental competence was not essential to the judgment approving the C & R Agreement nor material to the adjudication that did so.
However, with a petition to set aside an agreement under section 413(a) of the Act, the WCJ must determine whether a material mistake of fact or law was made when the agreement was executed. Russo v. Workers’ Compensation Appeal Board (Mon/Val Resources, Inc.), 755 A.2d 94 (Pa.Cmwlth.2000), appeal denied, 565 Pa. 658, 771 A.2d 1292 (2001); Hartner v. Workers’ Compensation Appeal Board (Phillips Mine & Mill, Inc.), 146 Pa. Cmwlth.167, 604 A.2d 1204, appeal denied, 531 Pa. 662, 613 A.2d 1210 (1992). Thus, in the proceeding to set aside the C & R Agreement, WCJ Getty was to determine, based upon evidence presented at the set aside hearing, whether the approved C & R Agreement contained or was based on information that was false or materially incorrect. It was in this hearing that the issue of Claimant’s mental competence was to be litigated, and Claimant proposed to offer expert medical testimony on that issue for WCJ Getty to consider. Because the issue before WCJ Getty is different from that considered and ruled upon by WCJ Desimone, I would hold that WCJ Getty erred in dismissing Claimant’s Petition based on collateral estoppel.
*1129The majority acknowledges this court’s recent decision in North Penn Sanitation Inc. v. Workers’ Compensation Appeal Board (Dillard), 850 A.2d 795, (Pa. Cmwlth.2004), in which we held that a C & R agreement may be set aside upon a clear showing of fraud, deception, duress or mutual mistake. However, the majority distinguishes Dillard, concluding that, while the claimant in that case was able to establish a mutual mistake of fact that warranted setting aside a C & R agreement, “Claimant’s alleged mental incapacity here does not constitute such a mutual mistake of fact.” (Majority op. at 11 n. 10.) I would submit that the majority’s distinction is unfounded and its conclusion premature. Like Claimant here, the claimant in Dillard testified that he understood the terms of the C & R agreement, and the WCJ made a finding to that effect; however, unlike Claimant here, he was afforded an opportunity to present evidence in support of his claim that this finding was a mistake.7
*1130As the party seeking to set aside the C & R Agreement, Claimant had the burden of proving that a material mistake of fact or law appeared in the C & R Agreement. Russo. At the hearing before WCJ Getty, Claimant sought to meet this burden through her own testimony and that of her treating psychologist. However, before Claimant was afforded the opportunity to do so, WCJ Getty dismissed Claimant’s Petition based on collateral estoppel. As stated, I believe this was error. Accordingly, I would vacate the WCAB’s order affirming WCJ Getty’s decision and order, and I would remand to the WCAB to remand to the WCJ for an evidentiary hearing and determination on Claimant’s Petition.
Judge SMITH-RIBNER joins in this dissent.
. Act of June 2, 1915, P.L. 736, as amended, added by, Act of June 24, 1996, P.L. 350, 77 P.S. § 1000.5.
. Section 449 of the Act provides, in relevant part, that the WCJ shall not approve any C & R Agreement unless he first determines that , the claimant understands the Agreement's full legal significance. 77 P.S. § 1000.5(b). In addition, the C & R Agreement must specify that the claimant is represented by an attorney of his or her own choosing or that the claimant has been specifically informed of the right to representation by an attorney of his or her own choosing and has declined such representation. 77 P.S. § 1000.5(c)(ll).
.In her brief to WCJ Getty, Claimant recounted the significant mental impairments she suffers as a result of her work-related injury, and she maintained that she acquiesced to the C & R Agreement only because Employer's insurer pressured her to accept a settlement of the claim. Claimant then argued that, because Employer failed to raise the issue of collateral estoppel in its *1127answer to the Petition, Employer had waived its right to assert that defense. Alternatively, Claimant argued that collateral estoppel did not apply because she did not have a full and fair opportunity to litigate in the proceeding before WCJ Desimone where (1) she was not represented by independent counsel and (2) her mental condition, of which Employer was aware, prevented her from understanding the significance of the proceeding or exercising a voluntary choice concerning the C & R Agreement. (R.R. at 21-27.)
. Claimant asserts that, contrary to representations in the Employee’s Certification portion of the C & R Agreement and to WCJ Desi-mone's Findings of Fact, No. 4, Claimant did not understand the full legal significance of the C & R Agreement at the time she signed that document. Moreover, Claimant asserts that, contrary to the C & R Agreement, she was not represented by independent counsel as required under section 449(c)(ll) of the Act.
. The WCAB’s own decision reflects this absurdity. Although affirming WCJ Getty's dismissal of Claimant’s Petition based on collateral estoppel, the WCAB nevertheless addressed the merits of Claimant’s argument that the C & R Agreement should be set aside because she did not understand the legal significance of the C & R Agreement and because she was not represented by an attorney of her own choosing at the C & R Agreement proceedings before WCJ Desi-mone. The WCAB determined that Claimant's argument was without merit. Pointing out that Claimant had not presented any evidence to support her allegations, the WCAB concluded that, absent evidence to the contrary, it had to presume that Claimant was represented by an attorney of her choice and that Employer was not guilty of any wrongdoing in connection with the C & R Agreement. However, in her appeal to the WCAB, and now to this court, Claimant specifically asserts that she was denied the opportunity to present evidence to prove her allegations.
.Collateral estoppel forecloses relitigation of an issue of law or fact that has been finally decided when the following factors are demonstrated: (1) the legal or factual issues are identical; (2) they were actually litigated; (3) they were essential to the judgment; and (4) they were material to the adjudication. Yonkers v. Donora Borough, 702 A.2d 618 (Pa.*1128Cmwlth.1997). The party against whom the plea is asserted must have been a party, or in privily to a party, in the prior action and must have had a full and fair opportunity to litigate the issue in question. Bortz v. Workmen’s Compensation Appeal Board (Reznor Division of FL Industries), 546 Pa. 77, 683 A.2d 259 (1996).
. In Dillard, the claimant received benefits for a work-related injury pursuant to a Notice of Compensation Payable, which designated the injury as a fractured skull, body contusions and lacerations. Approximately nine years later, the claimant and employer executed a C & R agreement whereby the claimant would receive $50,000 for the final settlement of all claims related to the designated work injury. At the hearing for approval of the C & R agreement, the claimant testified regarding his understanding of the document. Based on that testimony, the WCJ specifically found that the claimant “understood the full legal significance and import of the [C & R afgreement,” op. at 796(emphasis added), and issued an order approving the agreement.
Subsequently, the claimant filed a petition to set aside the C & R agreement on grounds that he had sustained work-related blindness that was not included in the C & R agreement’s description of his injury. At the hearing on the set aside petition, Claimant acknowledged that he made no mention of his blindness at the prior hearing on the C & R agreement, and Claimant admitted that he responded "yes” when asked if he understood the terms of the C & R agreement. Nevertheless, the claimant was allowed to testify and present medical evidence in support of his petition to set aside the agreement, and the WCJ ultimately concluded that the C & R agreement was based upon a material mistake of fact and should be set aside.
The employer appealed, and, similar to Employer in the present case, argued that once a C & R is lawfully executed and approved pursuant to the Act, it is final, conclusive and binding upon the parties. We disagreed, concluding that "it would be illogical to give a WCJ authority to approve a compromise and release but no authority to rescind his action.” Op. at 799. We then determined that the claimant successfully established that a mutual mistake of fact existed at the time the C & R agreement was executed, and, therefore, the WCJ did not err in setting aside that agreement. In doing so, we also stated:
Additionally, we note that [the claimant's work-related blindness was not disclosed to WCJ Shayhorn. In approving the parties' [ajgreement, WCJ Shayhorn relied upon the representation that [the cjlaimant's injuries were fully disclosed, when they were not. Since WCJ Shayhorn was unaware of [the cjlaimant’s condition, it was impossible for the judge to ascertain whether [the cjlaim-ant understood the full legal significance of the [ajgreement. Given the nature of [the cjlaimant's injury and his inability to read the [ajgreement, [the cjlaimant was at a unique disadvantage. This disadvantage was further compounded by the fact that [the cjlaimant did not receive independent legal advice.... Under these circumstances, we cannot conclude that WCJ Dev-lin abused his discretion in setting aside the Agreement. In rendering this decision, we keep in mind that the Act is remedial in nature and intended to be liberally construed in favor of an injured employee, i.e., to effectuate its humanitarian purpose.
Op. at 801 (footnote and citation omitted).
Like the claimant in Dillard, Claimant here seeks to testify and present medical evidence to prove that, notwithstanding her testimony during the C & R Agreement approval hearing, she did not understand the full legal significance of the C & R Agreement at the time it was executed. Moreover, as in Dillard, Claimant asserts that Employer was aware of her mental incapacity but did not disclose this to WCJ Desimone. I can discern no distinction between whether that claimed lack of understanding results from a visual *1130impairment, as in Dillard, or whether it is due to a mental impairment, as alleged by Claimant here. Indeed, I believe that if the majority's collateral estoppel analysis had been applied in Dillard, the claimant there would have been precluded from challenging the WCJ's finding that he understood the terms of the C & R agreement, a result at odds with the humanitarian purpose of the Act.