Mesothelioma claims: Key lessons on apportionment, late evidence, and witness memory

A recent decision of the Court of Session, Reid v MCM Building & Anr [2026] CSOH 34, provides guidance for parties involved in asbestos/mesothelioma litigation. Although fact-specific, it highlights practical points on contribution between defenders, the risks of late productions, and how courts may assess witness evidence where events occurred many years earlier.

Background

The court heard evidence that the pursuer had been exposed to asbestos while working as a labourer for two employers between 1999 and 2003. He had since been diagnosed with sarcomatoid pleural mesothelioma and alleged his employments had caused or materially contributed to his condition. The proof was restricted to the issue of liability.

Liability was established against both defenders, who were found jointly and severally liable for damages. The court found the pursuer to be both credible and reliable. The court found exposure would amount to a material increase in risk (in line with Fairchild principle and s.3(2) of the Compensation Act 2006). The court then considered how liability should be apportioned between the defenders.

Apportionment

The court did not simply apportion by reference to time employed (often described as a “time on risk” approach). It assessed the likely intensity and duration of exposure in each employment. On the evidence, the pursuer’s exposure with the first defender was limited (at most around one and a half days removing asbestos roofing), whereas exposure with the second defender was likely to have occurred repeatedly throughout the employment (including regular handling of asbestos waste).

The court therefore assessed relative exposure by reference to estimated fibre concentrations over time (expressed as fibres/ml years). On that analysis, contribution was apportioned very heavily against the second defender (99.908%), with a very small share (approximately 0.092%) allocated to the first.

You may ask, given the limited extent of the first defender’s share; why did they not argue that any contribution it made to the pursuer’s condition was de minims (too small to be meaningful). It seemed the first defender did intend arguing at one point that any exposure with them was de minimis but they did not attempt to run the argument at submissions which may at least in part it seems because of the exclusion of late productions – see below.

Other Key Takeaways

The case however raised several other interesting issues.

1) Late evidence is high risk

On the first day of proof, the first defender sought to lodge additional material (including expert occupational hygienist evidence and guidance material). Their reason for delay was that they did not know what the pursuer’s evidence would be until he gave evidence on commission in November 2025. It will not escape many reading this, that in Scotland, it is not unusual not to know what the evidence of a living pursuer is, until they give oral evidence at proof.

The motion was refused as it came too late, which serves as a practical warning to any party, seeking to reply on expert evidence. If expert evidence is required, then ensure experts are identified, and reports are instructed, disclosed and lodged in good time.

2) It’s not enough to challenge witness reliability on the passage of time alone

The second defender sought to challenge the evidence given by the pursuer relying on “frailty of human memory and the unreliability of eyewitness testimony” to cast doubt on the evidence regarding exposure to asbestos. In doing so they relied on the comments in Gestmin SGPS SA v Credit Suisse (UK) Ltd [2013] EWHC 3560 (Comm); [2020] 1 CLC 428 and subsequent cases.

The court accepted the general point that recollection can be reconstructed and influenced over time. However, it noted that Gestmin arose in a commercial context where contemporaneous documents are often available, and that approach is less helpful where there is little or no documentary record – and in the present case the court was not being asked to consider contradictory documentary evidence. The court placed weight on the pursuer’s account of repetitive working practices and accepted his evidence on the key issues.

Although it is not a failsafe method of challenging witness credibility in asbestos on the grounds of human memory, and the passage of time – if defenders want to attempt to, they ought to lead positive evidence which seeks to contradict the evidence lead on behalf of the pursuer

3) Affidavit evidence as evidence in chief may be admissible

As mentioned, the pursuer’s evidence had been taken, prior to proof, on Commission in November 2025 – presumably due to his heath. He was however available and fit to give evidence at fit and sought to adopt his affidavit as evidence in chief supplemented by further oral evidence, and cross examination in the usual way.

This was challenge by the first defender, on the basis that his oral evidence in chief had been elicited by leading questions taking him through the affidavit. The court did not accept that criticism noting that the pursuer expanded meaningfully on his affidavit and was cross-examined.

While there is undoubtedly scope for cross-examination regarding the way in which affidavit evidence is taken; the case serves as a reminder that affidavit may always be admissible as evidence and it is still open to the court to decide how much weight to put on that evidence.

What this means for businesses and insurers?

For defenders, the decision reinforces the value of early investigation and evidence gathering, including occupational hygiene input where appropriate. It also highlights that (a) contribution outcomes may be driven by evidence of intensity of exposure rather than time alone, and (b) challenges to witness evidence must be rooted in the procedural history and the available record, not general assertions about memory.

If you would like to discuss the contents of this article further, please get in touch with our insurance team, or your usual Brodies contact.