What Is the Section 20(a) Presumption?
Section 20(a) of the Longshore Act (33 U.S.C. 920(a)) creates a rebuttable presumption that an employee's injury is causally related to their employment — but only after the worker establishes a prima facie case. This presumption is strictly procedural: it shifts the burden of proof on causation to the employer, but it is not evidence itself and does not strengthen any party's evidence.
A common misunderstanding arises from the statute's language, which states it presumes "the claim comes within the provisions of this Act." Courts do not interpret Section 20(a) as a presumption of coverage regarding situs or status under the LHWCA. Instead, it presumes the injury "arose out of" employment as defined in Section 902(2).
Prima Facie Case Triggers the Presumption
The Section 20(a) presumption does not activate automatically. A claimant must first build a prima facie case by proving two elements: (1) they suffered some harm or pain, and (2) working conditions existed or an accident occurred that could have caused that harm. This is the claimant's independent burden — the presumption itself does not help establish the prima facie case.
Evidence for this step typically includes medical records documenting an injury, accident reports, witness statements, or an email reporting the incident to a supervisor. The threshold is relatively low, but it must be met with concrete proof, not speculation.
Actual Exposure Required
A mere suggestion of possible exposure to harmful conditions does not satisfy the standard. In Curran v. Thorpe Insulation Corporation, the Benefits Review Board held that the claimant must present specific evidence establishing that the worker was actually exposed to the harmful condition. General claims that working conditions "could have" caused the injury are insufficient to invoke the presumption.
Consequential Injuries Follow the Same Rule
The Section 20(a) presumption also applies to consequential (secondary) injury claims, but the claimant must produce some evidence that the primary injury could have naturally or unavoidably caused the secondary injury. The Fourth Circuit confirmed in Metro Machine Corporation v. Director, OWCP that this is a disjunctive requirement — the secondary injury can be caused naturally or unavoidably.
For both primary and consequential claims, the quality and specificity of the initial medical documentation often determines whether the prima facie case holds. Our physicians at NorCal Medical Consulting conduct independent medical evaluations and chart reviews that align with OWCP standards, helping ensure that the evidence presented — whether for the claimant or the defense — meets the evidentiary threshold required from the outset.
Burden Shifts: Employer Must Rebut
Burden Shifts: Employer Must Rebut:
Once the injured worker establishes a prima facie case, Section 20(a) of the Longshore and Harbor Workers' Compensation Act presumes the harm was causally related to employment. This presumption does not prove causation on its own. Instead, it acts as a procedural tool that shifts the burden of proof to the employer on the issue of causation.
The employer must produce "substantial evidence" to rebut the presumption. This standard is defined as "such relevant evidence as a reasonable mind might accept as adequate to support a conclusion." The most common form is a medical opinion stating, to a reasonable degree of medical certainty, that the harm is not related to the worker's employment. Our team at NorCal Medical Consulting frequently provides these independent medical evaluations for defense counsel.
If the employer produces substantial evidence, the Section 20(a) presumption "disappears." The adjudicator then decides causation based on the entire record, with the claimant bearing the ultimate burden of persuasion by a preponderance of the evidence. If the employer fails to rebut the presumption, the claimant wins on the causation issue, and no further evidence on that point is needed.
What 20(a) Does and Does Not Cover
Section 20(a) of the Longshore and Harbor Workers' Compensation Act creates a presumption that applies to all claim types: medical-only, death, occupational disease, aggravation, and consequential injuries. Once a claimant establishes a prima facie case, the presumption links the harm to employment regardless of the injury category.
But the presumption has firm boundaries you need to know. Section 20(a) does not help establish the prima facie case itself. It does not determine the nature of disability (temporary vs. permanent) or the extent of disability (partial vs. total).
It does not support the reasonable and necessary requirement for medical treatment. For survivor's benefits, it only presumes the death was employment-related; it does not establish a claimant's eligibility for those benefits.
You should note that the presumption attaches only to injuries specifically claimed on the Longshore Act claim form. In one notable ruling, an appeals court reversed a judge's decision to apply Section 20(a) to a heart condition allegedly caused by steroid use for a back injury, because the heart condition was never listed in the initial claim. The worker had to prove that the new condition naturally or unavoidably resulted from the primary injury.
The zone of danger test from tort law does not apply to LHWCA claims. As the Fourth Circuit held in Ceres Marine Terminals, the Act does not distinguish between psychological and physical injuries. A psychological injury claim does not require accompanying physical harm or threatened physical harm. This means Section 20(a) can apply to stand-alone psychological injury claims as long as the prima facie case is established.
Claimant Credibility and the Presumption
Section 20(a) is a procedural tool, but it does not operate in a vacuum. An Administrative Law Judge (ALJ) has exclusive authority to weigh evidence and make credibility determinations. If an ALJ finds a claimant's testimony so unworthy of belief that it cannot support the initial prima facie case, the Section 20(a) presumption is never triggered. The Fifth Circuit has affirmed this principle: the ALJ may assess credibility at the threshold, and the Benefits Review Board (BRB) was reversed for ignoring this step.
Surveillance video is one of the most effective tools for preventing or rebutting the presumption. When video shows a claimant performing activities without pain or limitation — contradicting their sworn testimony — it can serve as substantial evidence to rebut the presumption. If a claimant provides multiple inconsistent versions of the accident, an ALJ can find the assertions inadequate to invoke Section 20(a) in the first place.
Credibility concerns also affect the weight of medical evidence. In the SALAAM case, the claimant testified he had no prior left knee pain, but records showed two evaluations in 2019 for the same issue. The treating physician relied on the claimant's inaccurate self-reporting, so the ALJ gave greater weight to the employer's experts — a physiatrist and an orthopedic surgeon — whose opinions had rebutted the Section 20(a) presumption after credible review of prior records. In the Kkunsa case, the claimant's own alleged amnesia and inconsistent reports further undermined the treating provider's opinion because that opinion was based entirely on the claimant's narrative.
An OWCP-appointed examiner's report is not dispositive. Under Ceres Marine Terminals, any such report must be weighed alongside all other medical evidence of record. A well-supported opinion from a defense-retained expert who reviews the full record, conducts objective testing, and interviews the claimant can carry greater weight than a treating physician's opinion when the treating doctor relied on inaccurate self-reporting.
For practitioners, this means the path to rebutting Section 20(a) often runs through an aggressive investigation of the claimant's prior records, surveillance, and consistency of statements. NorCal Medical Consulting provides independent medical evaluations and chart reviews designed to withstand credibility scrutiny, with thorough documentation that holds up whether the presumption is in play or has been successfully rebutted.
Practical Steps for Defense Counsel
The Section 20(a) presumption gives the claimant a procedural advantage on causation, but defense counsel can overcome it with the right strategy. The most effective approach begins well before any hearing: develop substantial evidence early.
Obtain a medical opinion from a qualified physician that states, to a reasonable degree of medical certainty, that the claimed harm is not causally related to the claimant's employment. This is the most common form of "substantial evidence" that rebuts the presumption and makes it disappear.
Surveillance footage that objectively contradicts a claimant's reported pain or physical limitations can also constitute substantial evidence. The Fifth Circuit has recognized that an ALJ may reject a medical expert's opinion if it conflicts with observable evidence like video showing the claimant performing activities without limitation.
Scrutinize the claimant's version of events for inconsistencies. Multiple shifting accounts of the accident or injury can defeat the prima facie case entirely. In a Fifth Circuit case, an ALJ was allowed to find the claimant's assertions so unworthy of belief that they were inadequate to invoke the Section 20(a) presumption in the first place.
When securing an Independent Medical Evaluation (IME), ensure it is thorough, well-reasoned, and based on objective testing. The Kkunsa case demonstrated that a strong defense expert can outweigh a weak treating source. The defense's neuropsychologist, who reviewed all records, spent considerable time interviewing the claimant, and conducted significant testing, carried more weight than the claimant's treating provider whose records were illegible and lacked specifics.
The defense expert must review all available records and provide more than conclusory statements. The Benefits Review Board will favor a reasoned, documented opinion over a bare assertion. Our team at NorCal Medical Consulting conducts IMEs that are built to withstand Daubert challenges and Federal Rule of Evidence 702 scrutiny, from initial file review through deposition and trial.
Practical Steps for Claimant Counsel
A strong Section 20(a) strategy begins before the claim is filed. Ensure the initial claim form (LS-201 or equivalent) identifies every claimed condition with specificity — the presumption only applies to injuries explicitly listed. In one case, a worker who claimed back and groin injuries could not use Section 20(a) to later include a heart condition the judge had presumed was work-related, because the heart condition was not on the initial form.
Document the prima facie case with concrete evidence: medical records showing the harm and proof of workplace conditions or an accident that could have caused it. General assertions of possible exposure are not enough. The claimant must present evidence that the worker was actually exposed to the harmful condition.
For secondary conditions, produce evidence that the primary injury could have "naturally or unavoidably" caused the secondary condition. This standard is disjunctive, meaning either "naturally" or "unavoidably" can satisfy it. The same rule applies when claiming a consequential injury follows from the primary work injury.
A treating physician's opinion carries special weight if the claimant is credible. If credibility is undermined — for example, by inconsistent testimony or surveillance evidence — the defense's expert may prevail. In Salaam v. Ceres Marine Terminals, Inc., the claimant denied having prior left knee pain despite evidence of two earlier evaluations, and his treating physician relied on that inaccurate history. The ALJ gave greater weight to the defense's experts, and the BRB affirmed.
Remember what Section 20(a) does not cover. It does not help prove the nature or extent of disability (temporary versus permanent, partial versus total) or the reasonable and necessary requirement for medical treatment. Those elements must be proven independently through medical records and expert testimony. Our team at NorCal Medical Consulting routinely prepares medical evaluations that satisfy this independent burden, providing objective, evidence-based opinions on disability ratings and treatment necessity.
Pitfalls to Avoid with Section 20(a)
Section 20(a) does not create a "presumption of coverage." It cannot help a claimant prove situs or status — those elements must be established independently. The presumption only addresses the causal link between an injury and employment.
The presumption disappears entirely once the employer produces substantial evidence rebutting causation. At that point, the adjudicator decides based on all evidence in the record, and the claimant bears the ultimate burden of persuasion by a preponderance of the evidence.
Section 20(a) is not evidence. It does not strengthen the weight of evidence for any party. It is strictly a procedural tool that shifts the burden of production on causation from the claimant to the employer.
For consequential injuries, a mere temporal relationship is not enough. In the Kkunsa case, a doctor's note stating symptoms "followed working in Iraq" was found to establish only a time sequence, not a causal connection. The Benefits Review Board affirmed that the claimant failed to prove a work-related psychological condition.
Employers must raise the statute of limitations defense at the first hearing. In Newcomer v. Dyncorp International, the BRB clarified that an informal conference is not a "first hearing." Failure to raise the defense at the proper hearing results in a waiver.
Final Takeaway
Section 20(a) is a useful but narrow procedural tool. It addresses only causation and only after you establish a prima facie case. Success in any LHWCA claim depends on the quality of medical documentation, a thorough investigation, and strong witness credibility.
At NorCal Medical Consulting, our physicians conduct evaluations aligned with OWCP standards from the initial file review, providing independent, Daubert-compliant reports that hold up whether the presumption is invoked or rebutted.
