Blameworthiness or causative potency – which, if either, carries more weight when apportioning responsibility for injury?

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Blameworthiness or causative potency – which, if either, carries more weight when apportioning responsibility for injury?

Published 21 July 2022

Two recent decisions from Scotland look at apportionment between co-Defendants where there is a clinical negligence element to the claim.

The majority of reported cases which assist us in considering apportionment arise from contributory negligence proceedings as between a pursuer and defendant, rather than between multiple defendants who have each contributed to the damage or harm sustained by another party in some way.  In both scenarios, the apportionment of liability between different parties is not a straightforward matter.

Hobhouse LJ said in Downs v Chappell [1997], “The extent of a person’s responsibility involves both the degree of his fault and the degree to which it contributed to the damage in question. It is just and equitable to take into account both the seriousness of the respective parties’ faults and their causative relevance.”

But which of these two considerations, ‘blameworthiness’ or ‘causative potency’, should carry more weight when apportioning responsibility between defendants? And what does each of these concepts actually mean?

The case of Widdowson's Executrix v Liberty Insurance Ltd & Ors [2021] considered this issue.  A passenger was seriously injured in a road traffic accident and died 11 days later in hospital.  The first defender (a motor insurer) admitted liability for its insured, who was driving around a corner at excess speed – this is what caused the accident.  The second and third defenders (NHS Boards) admitted liability for adopting too conservative a plan of treatment and ultimately failure to prevent the cardiac arrest from which the deceased sadly did not recover.

It was not in question that the deceased's life-threatening injuries had been caused by the fault of the first defender’s insured.  However, there were opportunities thereafter to save his life. Had surgery been performed timeously, on balance the deceased would have survived. 

Bearing this in mind, it might be  assumed that the greater responsibility for the ultimate outcome would fall to the second and third defenders.  Indeed, those acting for the first defender argued that whatever the ‘blameworthiness’ of their insured due to the nature of the accident, his ‘causative potency’ in terms of the death was “almost nil” as it had been “considerably diluted by the significant medical failings at the hospitals”.

The Judge hearing the case, Lady Wise, noted that the first defender’s insured was likely to have been driving in excess of 80mph, well above the speed limit, at the point of the collision.  It was considered that his driving was “extremely reckless” and that he would almost certainly have been prosecuted had he survived.   The evidence pointed to the second and third defenders both doing their best to care for a patient, with the failings being essentially “honest mistakes”.   There was no evidence of reckless behaviour or an uncaring approach on their part. 

Ultimately, the high degree of blameworthiness on the part of the first defender’s insured, which involved a positive act on his part in driving too fast for the road, appears to have been the primary consideration of the court.  The behaviour was noted to stand out as being “morally reprehensible”.  This was contrasted with the fault of the second and third defender’s medical teams, who had tried their best for their patient, with their negligence being that of omission.   

As such, in respect of ‘blameworthiness’, the court was clear that by far the most significant fault attached to the first defender.

In regards to ‘causative potency’, the court considered that whilst the actions of the first defender’s insured was also greater than that of the omissions of the medical professionals involved thereafter, the disparity between the parties was not as significant as the disparity that was present in regards to ‘blameworthiness’.

Ultimately, the Court held that it was ‘just’ to apportion the greatest proportion of blame to the first defender’s insured – the actions of whom triggered everything that followed, and who was the only party that acted without any care for the ultimate consequences of his actions.  Liability was apportioned at 70% to the first defender and 15% to each of the second and third defenders.

As such, the indication is that ‘blameworthiness’ as opposed to ‘causative potency’, carried more weight when apportioning liability between the defendants in this case.  Both the ‘moral culpability’ and the ‘actions’ of the parties seem to have been relevant factors when considering ‘blameworthiness’.  The fact that the negligence of the first defender’s insured involved a positive act whereas the negligence of the second and third defenders was one of omission only were noted to be factors in considering respective ‘blameworthiness’, albeit the moral culpability of the parties seems to have been of most relevance to the court when considering this issue.

The relative importance of ‘blameworthiness’ and ‘causative potency’ was again considered in the case of Almond-Roots v Eljamel & NHS Tayside [2021].  That was a slightly unusual case as it involved one surgeon acting both in a private capacity and also for the NHS. 

In short, there were delays by the second defenders in reaching a diagnosis of cauda equina syndrome (CES) following assessment.  An MRI scan was arranged but not on an urgent basis, causing a delay of around 2 weeks.  Had CES been identified at the appropriate time, surgery would have been undertaken which on balance would have been predominantly successful.  However, the pursuer elected to undergo surgery on a private basis with the first defender.  This surgery was performed negligently and the response to the pursuer’s deteriorating condition following the surgery was also negligent.

The first defender argued for a 50:50 apportionment. His position was that there was significant causal potency in the first act of negligence by the second defenders, i.e. the failure to carry out an urgent scan, which would have resulted in the performance of an operation which would have allowed the pursuer to live what would have been, to all intents and purposes, a normal life.  The argument was:

In respect of culpability and blameworthiness there was little to choose between the failings of the first defender when he was employed by the second defenders and his failings when he treated the pursuer as a private patient. Each consisted of a failure to meet the requisite standard of care of a reasonably competent neurosurgeon exercising reasonable skill and care’.

The position of the second defenders was that full responsibility should fall to the first defender. Whilst the second defenders relied on various earlier cases drawing a distinction between acts and omissions (see Poole Borough Council v GN [2020] AC 780 – “a distinction falls to be drawn between causing harm (making things worse) and failing to confer a benefit (not making things better)” and Thompson v Toorenburgh (1973) 50 DLR (3d) 717 - “Failing to take positive action which would have avoided an outcome is not the same as committing an act which directly causes harm”), it was the argument that its failures did not directly cause the outcome - the first defender’s surgery did - which was ultimately persuasive.

The judge concluded that it was correct to say any negligence by the second defenders did not cause any significant harm to the pursuer and that the ‘causative potency’ in relation to the neurological harm suffered as a result if their actions was nil.  Lord Uist said:

The negligence for which they were responsible was part of the sequence of events leading up to the serious negligence of the first defender which caused the nerve root injury. All new neurological deficits appeared after the operation carried out by the first defender on 16 April 2013: there was no major neurological deterioration before then.

Lord Uist found in favour of the second defenders and apportioned damages to be paid at 100% by the first defender and 0% by the second defenders.

Of interest in this case is the fact that the judge found it entirely unhelpful to draw a distinction between negligent acts and omissions.  He noted that an omission, particularly in the field of clinical negligence, is capable of causing serious harm or even death.

Rather, he considered that what matters is the ‘moral blameworthiness’ and ‘causative potency’ of the negligent act, whether it be a positive act or omission.  In this case, he felt that the ‘causative potency’ of the negligent act, whether it be a positive act or an omission, was key.  The negligent act of the second defenders did not cause any significant harm to the pursuer and did not cause her any neurological deterioration.  Essentially, the ‘causative potency’ for which the second defenders was responsible was nil. 

Of note is the fact that ‘blameworthiness’ considerations did not feature in this decision at all.  This is likely to be due to the facts of this particular case, where the actions for which first and second defender were responsible were essentially those of the same person. 

Ultimately, and perhaps unhelpfully in practical terms, it is clear that each case will be judged on its own facts and circumstances, with the aim being to find the true cause of an adverse outcome.  ‘Blameworthiness’ was the key factor in determining apportionment in the Widdowson's Executrix case, whereas ‘causative potency’ was the determining factor in the Almond-Roots case.

The differentiation between ‘positive acts’ and ‘omissions’ as seen in previous cases may be of less relevance going forward, with ‘blameworthiness’ considerations perhaps shifting more towards an analysis around moral culpability.   Both cases make it clear, however, that the focus of the court will remain on ‘blameworthiness’ and ‘causative potency’ when determining apportionment, meaning that you will need to consider each of these issues and apply whichever ‘fits’ best to the circumstances you are addressing.



Vicky Clarke

Vicky Clarke

+44 (0) 113 251 4972

Rachel Rough

Rachel Rough


+44 141 223 8550

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