The Mystery of Res Ipsa Loquitur: The Shifting of the Onus of Proof After Hanrahan

Enshrined in the Supreme Court Judgment of Hanrahan v Merck Sharpe & Dohme,[1] is Mr. Justice Henchy’s statement that on the ‘question of causation … mere difficulty of proof does not call for a shifting of the onus of proof.’ This discussion will be limited to tort law to better explore the judicial flexibility courts engage in to alter the requirements of the ‘but for’ test. Ultimately, I advocate that his proclamation does and should represent Irish tort law.

Conceptual and Evidential Elements

Typically, the onus of proof in tort law cases rests on the claimant. There are two elements to the test of causation: the conceptual element or what the claimant must prove, followed by the evidential element which is the standard to which it must be proven.[2] Applying this, the orthodox approach normally requires the claimant to satisfy the ‘but for’ test on the balance of probabilities. Simple applications of the ‘but for’ test revolve around the question of whether in the absence of the defendant’s actions, the claimant would still have suffered the loss. Regarding the standard of proof, it is not necessary for the claimant to categorically show that the defendant must be found guilty of negligence, but rather to convince the judge with evidence on a balance of probabilities.[3] However, as it can be seen in medical negligence cases, proving causation through the ‘but for’ test becomes increasingly problematic when there exists more than one possible cause. Hence, when hardship of proof arises, courts are compelled to provide alternatives and offer flexibility for causation. Although this flexibility can, for example, result in a lower standard of proof such as the material contribution or material risk conceptions applied in Fairchild,[4] mere difficulty alone is insufficient to shift the onus of proof to the defendant.

Transcending Mere Difficulty

As explored in Hanrahan, mere difficulty of proof does not go far enough to shift the onus of proof. Rather, the court stated that they would only allow a shifting of the onus when the defendant holds exclusive knowledge combined with the evidence being peculiarly within the defendant’s capacity of proof.[5] This sentiment was followed in Rothwell v MIBI,[6] where the claimant was unable to establish who caused the oil spillage leading to the car crash. Despite acknowledgement of the academic criticism concerning Hanrahan, Mr. Justice Hardiman interpreted the precedent as ‘authoritative unless and until specifically considered in a case where its reversal is sought.’[7]

The mentioned academic criticism partially stemmed from Mr. Justice Henchy’s controversial restatement of Res Ipsa Loquitur. The doctrine has been described as ‘one of the great mysteries of tort law,’ which may have been exacerbated by the judgment in Hanrahan.[8]

Res Ipsa Loquitur, which was established in the case of Scott v London,[9] essentially states that where an accident occurs under the management of the defendant which would not have normally occurred whilst using proper care, this is reasonable evidence to draw inferences of negligence. In other words, the principle is the ability to prove negligence by inference when the facts speak for themselves. For instance, the doctrine did not apply in Rothwell as the oil spill could have occurred without negligence. That is to say, that rather than the driver leaving the diesel cap off, it may have been for example, the fuel depot staff.[10] Contrastingly, the doctrine was scarcely applied in the case of Lindsay v Mid-Western Health Board,[11] where a failure to return a patient to consciousness called for an explanation from the defendants. However, the court did urge caution in requiring unreasonable proof from defendants. The defendant should only be required to show that they exercised all reasonable care rather than proving on a balance of probabilities that they did not cause the brain damage.[12]

Moreover, the court in Lindsay mentioned that the Latin phrasing of Res Ipsa Loquitur gave false notions that it was a special rule of substantive law rather than an aid in evaluating evidence. Further, Mr. Justice Murphy in Cosgrove v Ryan,[13] refused to shift the burden to the defendant as ‘the burden of casually linking the damage caused by the conduct of the defendant remains with the claimant, quite irrespective of the question of negligence.’[14]

Overall, unique circumstances such as those where the defendant has exclusive knowledge peculiarly within their capacity of proof, or scenarios where the Res Ipsa Loquitur doctrine applies, may serve to shift the onus of proof.

Judicial Flexibility

In order to assess whether Henchy J’s statement should represent Irish tort law, it is necessary to examine the flexible alternatives the English and Irish courts have been willing to implement instead of shifting the onus of proof. For instance, in McGhee v National Coal Board,[15] the conventional ‘but for’ test was modified to overcome ‘the insurmountable burden of proof that the orthodox test presented for the claimant.’ Hence, the House of Lords deemed that the claimant merely had to show that the defendant’s actions materially increased the risk rather than materially contributing to the occurrence on a balance of probabilities.[16]

These alternative approaches to ‘but for’ causation were further expanded in Fairchild v Glenhaven Funeral Services.[17] Issues arose due to the fact that the claimant had already been exposed to asbestos dust from multiple past employers and hence, it was scientifically impossible for the claimant to prove the origin of the single causative fibre.[18] The House of Lords found for the claimant and ruled more akin to McGhee. Whilst McGhee established that it was legitimate to infer from facts that the defendant’s breach of duty contributed to the development of disease, Fairchild went even further. The court in Fairchild claimed that proof of a material increase in the risk of contracting the disease was  sufficient to satisfy the proof of causation required for liability altogether.

These English cases help lay the groundwork for analysis of the Irish Supreme Court decision in Quinn v The Mid-Western Health Board.[19] The Quinn case strayed away from the approaches in McGhee and Fairchild, instead opting for the more conventional ‘but for’ test. Mr. Justice Kearns confined Fairchild to its facts and suggested that a more relaxed requirement for causation would only arise in exceptional circumstances. In Fairchild, the cause of the lung disease was not in doubt, rather the issue was how a court should act in a situation where the limits of medical science prevented a claimant from identifying which of the many duty breakers were liable.[20] That is to say that it would succeed when the only possible cause of harm were the wrongs of the employers. Contrastingly, in Quinn there could have been a number of different factors which caused the harm. On the surface, it appears that the Irish court is adamant in not allowing the flexibility in Fairchild to be availed of easily. However, it is worthwhile to note that the commentary in Quinn was essentially obiter due to the case being decided based on the permissibility of a procedural approach.[21] Hence, as the facts in Quinn were not exceptional enough to pass the flexibility threshold of Fairchild anyways, the reluctance of the Irish court towards alternatives in causation perhaps is not as steadfast as one would think.

Conclusion

In conclusion, mere difficulty does not merit a shifting of the onus of proof. The hardship facing the claimant is required to transcend into an unworkable proof of causation stemming from the defendant’s exclusive knowledge or the defendant’s control, raising inference through Res Ipsa Loquitur. In order to assess the merit of shifting the onus of proof, one needs to observe the leeway implemented by the court when causation becomes difficult. There is a divergence regarding judicial flexibility when comparing the rulings from the House of Lords and the Irish Supreme Court. Although the case of Quinn appears to quell flexibility in causation, due to the conflicting facts with Fairchild, the door is not closed for Irish courts to develop a more lenient approach when a case with more sympathetic facts arises. However, as seen in England, this more relaxed proposal will likely compensate for the shortcomings of the ‘but for’ test rather than alter the onus of proof. To paraphrase Quinn, any approach which reverses the onus of proof is of such magnitude as to require intervention by the legislation or a full court. Although I would encourage the Irish courts to broaden its flexibility when exceptionally unprovable cases arise, I wholeheartedly would not suggest a measure as draconian as shifting the onus of proof when mere difficulty arises. Thus, I believe that Mr. Justice Henchy’s statement does and certainly should represent Irish tort law.

[1] Hanrahan v Merck Sharp & Dohme [1988] IESC 1.

[2] Sandy Steel and David Ibbetson, ‘More Grief on Uncertain Causation in Tort' (2011) 70 Cambridge Law Journal 451, 452.

[3] Connaughton v Minister for Justice and Anor [2012] IEHC 203.

[4] Fairchild v Glenhaven Funeral Services Ltd and Others [2003] 1 AC 32.

[5] Byran McMahon and William Binchy, Law of Torts (4th edn, Bloomsbury Professional 2015) 923.

[6] Rothwell v The Motor Insurers Bureau of Ireland [2003] IESC 16.

[7] William Binchy, ‘Recent Developments in The Law of Torts’ (2004) Judicial Studies Institute Journal, 59.

[8] McMahon, Binchy (n5) 903.

[9] Scott v The London and St Katherine Docks Company [1865] 159 ER 665.

[10] Binchy (n7) 59.

[11] Lindsay v Mid-Western Health Board [1992] IESC 4.

[12] Colin Jennings, Barry Scannell and Dermot F. Sheehan, The Law of Personal Injuries (2nd edn, Round Hall 2016) 3-28.

[13] Cosgrove v Ryan [2008] IESC 2.

[14] Binchy (n7) 57.

[15] McGhee v National Coal Board [1973] 1 WLR 1.

[16] McMahon, Binchy (n5) 613. 

[17] [2002] UKHL 22.

[18] ibid.

[19] [2005] IESC 19.

[20] ibid.

[21] supra (n19).