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The long-anticipated judgment in Abbott v Ministry of Defence has now been handed down. Kate Longson, who was instructed as junior counsel to the Ministry of Defence, summarises the key aspects of the judgment.
In 2021, Hugh James solicitors issued a Claim Form in the name of David Abbott and approximately 3500 other Claimants for military noise-induced hearing loss. Since that time, thousands more have been added to that claim form and many more thousands of claims have been brought or intimated by other firms of solicitors.
Those who have been following the case will already know that, in the run up to the trial which took place from October to December 2025, the parties selected six test cases to be used as a vehicle for resolving various generic issues concerning causation and quantum which arose across the cohort, breach of duty, limitation and various other issues having been compromised by way of a settlement matrix.
Of the six test cases selected, two settled immediately prior to trial, and two discontinued during the course of the trial. The two remaining cases, Jack Craggs and Christopher Lambie, fortunately covered all of the generic issues, allowing for their resolution by Garnham J in this lengthy and comprehensive judgment which favours the Defendant in a number of notable and material respects, not least on the issues of latency, synaptopathy and the reliability of military audiometry.
I intend, in due course, to produce a mini-series of blogs addressing the main generic issues, some of which have wider implications, individually. For now, the following will hopefully provide a helpful summary of the Court’s findings on the most pertinent issues, namely:
It had been the Claimants’ position that military audiograms are inherently less reliable than BSA compliant audiometry and that, whilst they may be suitable for screening purposes, they could not be used for the purposes of diagnosing or quantifying NIHL.
The Defendant had argued that the overwhelming majority of military audiograms were obtained in good faith and using appropriate equipment. There was accordingly a legitimate presumption of accuracy and where, as in the case of Mr Lambie, there was purposeful inaccuracy, such would likely be readily apparent.
The Claimant’s position was derived from the generic evidence of Prof Moore who had suggested in his report that there is “persuasive evidence to suggest that occupational audiograms obtained during military service are often unreliable”. However, as noted by the Court, that evidence was never identified and, by the end of the trial, the Claimants’ experts had conceded that military audiometry cannot be disregarded on a generic basis.
The Court’s conclusions ultimately favoured the Defendant:
233. It follows, that to a substantial extent, I accept the Defendant’s submissions on this issue. My conclusion, against the evidential background set out above, are as follows:
(i) Pure Tone Audiometry (PTA) conducted in compliance with the protocol and standards set by the British Society of Audiology (BSA) is the gold standard of audiometric testing and should be used in medico-legal cases as the best evidence whenever it is available.
(ii) However, screening audiograms, including military screening audiograms, are ordinarily suitable for screening and triage. Furthermore, especially when they are part of a consistent pattern, they may also be used, as part of the exercise of clinical judgment by clinicians advising in medico-legal cases, for diagnostic and quantification purposes.
(iii) It may be possible to obtain from screening audiograms an understanding of the hearing profile and trends of an individual (in other words his auditory capabilities and the changes in those capabilities) where there is a consistent pattern in an audiometric series. That may not be possible where the screening audiograms show significant and unexplained variation.
(iv) Audiometry evidence (including BSA-compliant PTA) should, wherever possible, be considered in context and as a whole, rather than in isolation.
(v) The arrangements operated by the MoD are designed to give a good degree of oversight over the hearing capacity of members of the armed forces. The majority of such audiograms are conducted properly and in good faith. This is particularly so once a referral for medical assessment is made. However, there may, on occasions, be systemic or operational inadequacies, or even deliberate falsehood, and the Court should be alive to that possibility.
The Court had before it four methodologies for the diagnosis of noise-induced hearing loss in a military context, three of which were authored principally by Professor Brian Moore and put forward by the Claimants, namely:
The final methodology considered was the method proposed by Coles, Lutman and Buffin (CLB) which has been in conventional use in cases of industrial noise exposure since the Nottinghamshire and Derbyshire Deafness Litigation. This was the method relied upon by the Defendant.
Having carefully set out the competing methods, the Court concluded that the M-NIHL method and MLP(18) method could be rejected in short order.
Dealing first with the M-NIHL method, the Court noted that this method had been superseded, two years after publication, by the rM-NIHL method. The revised method was necessitated by issues which had been identified with the specificity of the original method. Although he had said in evidence that the rM-NIHL method should be preferred, Prof Moore also suggested that, if the revised method was not met, it would be appropriate to go back to the original method to see if it yielded a positive diagnosis. As to that, the Court, having set out in detail the identified shortcomings in the M-NIHL method, concluded:
350. I unhesitatingly reject the suggestion that, all that notwithstanding, it might in certain cases be reasonable, if a case did not receive a diagnosis under rM-NIHL, to go back to the original method on the basis that it has a positive predictive value or ‘PPV’ greater than 0.5 (which, Prof. Moore said, indicates the balance of probabilities was met.). It was deficiencies in the original method, notably its tendency to produce false positives, that prompted the revised method and it would be nonsensical, if not improper, to seek to advance a case on the basis of what has been shown to be a deficient test, merely because the better test did not produce the desired outcome.
The MLP(18) method was addressed in similarly robust terms by the Court.
MLP(18) is a machine learning AI methodology which was trained by Prof Moore using a database of audiograms obtained by Claimants making claims for noise-induced hearing loss and a control database of Germans not known to have had significant noise exposure. It is fair to say that, during cross examination, Prof Moore conceded that it was not possible to tell why MLP(18) had given a diagnosis in a particular case:
Q. It gives a result, doesn’t it, that you can’t say why it has made a particular diagnosis in a given case? The output is still the black box?
A. That is true. That is true.
Q. So, for instance, an ENT surgeon who is using it couldn’t – wouldn’t be in a position to interrogate or challenge the result that comes out the other end?
A. Well, no – they wouldn’t – the result will come out positive or negative, they won’t know why…
Q. …with the individual case of Mr Craggs, for instance – his Lordship would not be in a position to understand why that number has come out the other end, would he?
A. That’s correct.
Mr Zeitoun, the ENT surgeon instructed by Mr Craggs, accepted in his evidence that he did not use the MLP(18) method because he did not understand it.
Ultimately the Court concluded that:
356. In my judgment, that inability to understand how a result was obtained, to interrogate the method to reveal its workings, makes MLP(18) entirely unsuitable as a means of establishing a case in litigation. For a judge to accept a diagnosis on the basis of MLP (18) would be a complete dereliction of duty. Unless the Court could be satisfied, on evidence, that the method was entirely reliable in every case, then it has at least to be possible for a Court to understand how the method produces the result where the outcome is disputed. The alternative would, furthermore, make an appeal against the conclusion impossible on any ground other than the total absence of underlying analysis, because the appellate Court would be equally unable to test the reasoning on which the conclusion was based.
The Court was accordingly left to choose between the CLB method and the rM-NIHL method.
In the course of the expert evidence it had been argued that the presence of noise damage at 8 kHz in cases of exposure to impulse noise might disguise a notch/bulge and lead to a false negative diagnosis using the CLB method. Conversely the rM-NIHL method accounted for the potential for loss at 8 kHz.
The Defendant pointed to the potential for rM-NIHL to reach a false positive diagnosis in cases of idiopathic hearing loss. However the Court, in reliance on its own findings about the reliability of military audiograms, was satisfied that cases of idiopathic hearing loss would be capable of identification.
The Learned Judge ultimately concluded as follows
418. I conclude, on the basis of all the evidence I have heard, that Mr Steinberg is right when he submits that military NIHL can present without a CLB notch/bulge and the absence of a notch does not exclude NIHL, that military noise commonly affects hearing at 8 kHz and this can erase or disguise a notch or bulge; and that military impulse noise tends to produce a different and more variable audiometric pattern than steady state noise.
419. It follows, first, that the original M-NIHL method and the MLP(18) method should not be relied on in medico-legal work (see [346] above and following; second, that CLB is not generally suitable in military cases and third that the rM-NIHL method is the method to be preferred. A proper diagnosis of NIHL depends on the careful application of each element of the rM-NIHL test.
In an earlier chapter, the Court had already concluded that there should be a baseline correction to the presbycusis data set out in the 2017/2024 ISO database and it is this data which should be used when determining both diagnosis and quantification.
The Court also concluded that it would not be necessary as a matter of course in every case to make the, now customary, 6 dB deduction at 6 kHz to account for the use of TDH-39 headphones.
The Court was presented with two competing methodologies for quantification: that proposed by Prof Moore and the “LCB” methodology which accompanies the CLB diagnostic paper.
In light of his findings as to diagnostic methodology, the Learned Judge favoured the quantification method proposed by Prof Moore with some important caveats:
Firstly, as to referent percentile, Prof Moore had suggested, both the MLC paper and in oral evidence, that the 50th percentile should be used as a default. He had suggested that a lower percentile should only be selected if a BSA complaint audiogram had been obtained prior to noise exposure and supported the use of a lower percentile (which would have the effect of reducing the amount of hearing loss which could be attributed to noise exposure). However he had supported the use of a higher percentile (which would give a more favourable result to the Claimant) where only one frequency in only one ear showed better than average hearing.
The Court held as follows:
474. Mr Platt was also correct in his submissions in respect of Prof. Moore’s 2022 paper. He said first that by “reliable” Prof. Moore means “BSA compliant”. It is clear that is what he meant. In cross-examination, Prof. Moore accepted that, in practice, it is “vanishingly rare” for an individual to have a BSA compliant audiogram taken prior to the start of military service, and indeed he had never seen such a case. But for the reason set out in chapter 6 that seems to me too stringent a position. Occupational audiograms should not be discarded and, particularly when part of a series, can provide good evidence of hearing ability. They should be so considered when considering the relevant percentile.
475. Mr Platt also makes a good point when he submits that the scheme advocated by Prof. Moore in MLC is unfairly constructed to favour Claimants. On the one hand, as Mr Platt submits, the likelihood is that in practice, a user of the Moore method would never adjust the percentile downwards and every individual on a percentile below the 50th would thus be overcompensated. But on the other, the percentile might be adjusted upwards (i.e. in favour of the Claimant) by the operation of paragraphs 2 and 3, if an individual shows better than average hearing at only one threshold and, if that threshold is in the better hearing ear, in only one ear. That is plainly unjustified.
476. In my judgment, the proper course is that the choice of the percentile in the relevant dataset should be dictated by the clinical judgment of the medicolegal ENT surgeon based on the hearing profile of the individual as ascertained from all the available audiometry.
Secondly, as to appropriate frequencies over which to calculate disability, the Claimants had sought to argue that the Court should depart from the conventional use of an average over 1, 2 and 3 kHz to an average over 1, 2 and 4 kHz. Having considered the literature at length, the Court concluded that:
498. …On the evidence I have seen, it is clear that the traditional 1, 2, 3 kHz average remains a reliable, if conservative, measure of hearing disability, supported by longstanding practice and by parts of the literature that continue to recognise its adequacy. At the same time, the scientific material relied upon by the Claimants, notably Smoorenburg and Moore, suggest that frequencies above 3 kHz, and 4 kHz in particular, play an important role in the perception of speech in noisy environments, sound localisation, and recognition of environmental sounds.
499. I conclude that, while the conventional 1, 2, 3 kHz average should continue to serve as a baseline descriptor, it is entirely legitimate to consider 1, 2 and 4 kHz, particularly where speech‑in‑noise difficulty is a prominent feature of a Claimant’s disability. It should be for the ENT expert to identify which metric best represents the Claimant’s disability. The modest numerical differences do not undermine the utility of either approach; rather, they indicate that both metrics should potentially be available to the Court, with the weight to be attached to each depending on the factual and audiometric circumstances of the individual Claimant.
The Claimants had sought to argue that exposure to impulse noise accelerates the future progression of age-associated hearing loss. The Defendant stood by the ‘orthodox’ view that noise damages hearing at the point of exposure.
This was an extremely significant issue in the litigation, particularly when taken together with the reliability of military audiometry, and is likely to be determinative of a significant number of claims in the cohort.
The Defendant’s position was accepted by the Court. The Learned Judge agreed that there is insufficient scientific evidence to support the notion that noise causes latent damage to hearing. The Learned Judge went on to conclude that:
554. I also agree with Mr Platt that even if the acceleration theory was sufficiently plausible as to be viewed as “probable”, which in my view it certainly cannot at present, it cannot properly be applied to the circumstances of any given case or individual. Furthermore, Mr Platt is right that even if the theory is demonstrable and a mechanism can be conceived whereby it could be identified in a given individual, there is no way in which accelerated loss can be accurately quantified in such a fashion as to make a secure foundation for any award of damages.
555. In those circumstances, it is my conclusion that the theory that hearing loss may continue to develop after exposure is plausible, intellectually coherent but a very long way from being proven in human beings. The orthodox view that hearing loss does not progress after exposure ceases has not, at least at yet, been displaced.
As set out by the judge at [557], the expression “cochlear synaptopathy” refers to a loss in the connections (‘synapses’) between inner hair cells in the cochlea, the part of the ear which detect sounds, and the auditory nerve fibres, which carry the signals from the inner hair cells to the brain. The relevance of this issue to this litigation is that such synaptopathy might lead to individuals experiencing hearing difficulties (sometimes referred to as ‘hidden’ hearing loss), even if they have audiometric thresholds within the normal range.
The alleged presence of cochlear synaptopathy has been used by Prof Moore in a number of cases to explain the presence of noise damage in individuals with normal audiograms. He also suggested that it was likely that both remaining lead Claimants had a degree of cochlear synaptopathy. The Claimants accordingly proposed that cochlear synaptopathy in the context of military noise, is both plausible and a potential contributor to speech-in-noise difficulty and tinnitus, and should be weighed accordingly.
The Defendant contended that for none of the lead Claimants (or anyone in the wider cohort), can noise-induced cochlear synaptopathy be (i) definitively demonstrated, (ii) persuasively demonstrated by proxy measures, (iii) quantified, (iv) disentangled from age-related synaptopathy, or (v) connected to any particular adverse effect.
In order to determine whether such a phenomenon could be proven in a particular individual, and indeed quantified/apportioned, the Court heard evidence from Professors King and Plack, Auditory Neuroscientists, whose evidence was taken by ‘hottubbing’.
The fundamental issue for the Claimants was that cochlear synaptopathy can only be diagnosed post-mortem and there has only been one study in this area, Wu et al 2021. Accordingly, there is no diagnostic gold standard for a living individual and, given that cochlear synaptopathy likely occurs with age, no way to know how much synaptopathy is to be attributed to noise exposure.
The Defendant’s arguments were accepted and the Court found as follows:
605. In conclusion, in my view the Defendants are correct when they submit that cochlear synaptopathy cannot definitively be demonstrated, let alone quantified, in humans before death. ‘Proxy measures’ of cochlear synaptopathy are less than certain and there is no gold standard test for the condition. Studies on military personnel suggest noise may lead to cochlear synaptopathy but there is no certainty of that and these studies have no application to the circumstances of individual Claimants. In any event, cochlear synaptopathy occurs with ageing in humans and there is no mechanism for stripping out ‘synaptopathy of ageing’ from ‘synaptopathy of noise exposure’ or of establishing that noise exposure made an identifiable difference to hearing ability either in the presence of audiometric hearing loss or in its absence.
It was common ground between the experts that tinnitus which begins during or shortly after noise exposure could be attributed to it. A question arose, however, as to the extent to which tinnitus which arose many years after cessation of noise exposure could be attributed to it. Having reviewed all of the evidence, the Court concluded that:
738. Tinnitus normally begins during exposure to noise or shortly after the cessation of noise. It is not possible to identify an arbitrary time after exposure to noise beyond which a claim should not be considered. The most that can be said is that the closer the onset of tinnitus is in time to the exposure to dangerous noise, the more likely it is to be caused by it. The longer the period between the end of exposure and the onset of tinnitus the greater should be the intensity of the examiner’s scrutiny of the circumstances of the case and the veracity of the informant. And the Court, faced with a disputed claim will have to be equally circumspect.
It was common ground between the ENT surgeons that a hearing loss of 4-5 dB would be clinically significant. It follows that a hearing loss of less than 4 dB, with no other consequences, should be considered de minimis:
681. A hearing loss of less than 4dB without other consequences should be regarded as de minimis. It will be a matter to be determined on a case-by-case basis whether exposure to noise which causes loss below that cut off nonetheless causes appreciable damage.
The Claimants had sought to argue that, where an individual is disabled by reason of their hearing loss, they will be entitled to damages for future loss of earnings calculated on an actuarial basis using the data set out in the Ogden Tables. It has become commonplace in these cases for large future loss of earnings claims to be advanced on this basis, including by individuals who were discharged from the military many years ago and who have suffered no past loss of earnings.
This issue arose specifically in the case of Mr Lambie who, having left the Royal Navy in 2021, has gone on to have a successful career as a management consultant in defence intelligence. Despite having suffered no past loss of earnings, Mr Lambie advanced a claim for £370,000 for future loss of earnings and pension, calculated on a multiplier-multiplicand basis.
The Learned Judge heard employment evidence on behalf of both parties, unhesitatingly preferring the evidence of the Defendant’s expert Mr Hailstone that, as regards future promotion prospects, it was Mr Lambie’s aptitude which was likely to dictate his career progression; not his hearing loss.
The Court ultimately concluded that to adopt a multiplier-multiplicand approach in this case would produce an obviously unreal result. Having considered the dicta of Jackson LJ in Billet v MOD, as well as the more recent judgment of Johnson J in Barry v MOD and other cases in which the applicability of the actuarial approach was discussed, the Court held:
852. In my view, Mr Lambie is disabled within the meaning of the Disability Discrimination Act 1995 but, his case is far from the average, even an “adjusted” average. His case is not one where it is appropriate to apply the 8th Ogden table. Unlike, for example, Mr Barry, Mr Lambie has been able to pursue his chosen career throughout and will, in all probability, be able to do so until retirement. His disability has not, thus far, affected the career choices open to him or the earnings he has been able to make. His hearing loss is serious and progressive with age, but as things currently stand, he is not suffering any loss of earnings, nor will he if, as seems likely, he remains in his current employment until retirement.
853. To award a man in Mr Lambie’s position the sort of sum proposed by Mr Steinberg would, in my judgment, be unconscionable. His current net take home pay is about £60,000. Including bonus but excluding pension, the sum claimed for loss of future earning amounts to more than six times his current annual net salary. And that for a man who has not been unemployed for a single day since he was 18, who is in steady employment with a reputable employer, whose work in under no threat and in respect of which there is no evidence of any future likely threat, who is highly valued by his current employers and who wishes to stay in his current job until retirement.
The Court recognised that Mr Lambie would be at a disadvantage on the open labour market and there was a residual risk that his future promotion prospects might be harmed by his hearing loss. A Smith v Manchester award of one year’s net salary was accordingly made.
It follows that the Courts are likely to be circumspect when dealing with claims for future loss of earnings advanced by those who have had lengthy careers following military discharge which have hitherto been unaffected by hearing loss, whether or not that hearing loss meets the criteria for disability.
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