Lachaux v Independent Print: How the Supreme Court Defined 'Serious Harm'

The 2019 Supreme Court decision in Lachaux v Independent Print Ltd [2019] UKSC 27 is the most important defamation judgment of the past decade. It fundamentally changed how claimants must prove their case under Section 1 of the Defamation Act 2013.

Background to the Case

Bruno Lachaux, a French aerospace engineer living in the UAE, brought defamation claims against the Independent and the Evening Standard over articles published in 2014. The articles reported allegations made by his ex-wife in the context of custody proceedings, including claims of domestic abuse and coercive control.

Mr Lachaux argued the articles were defamatory and had caused serious harm to his reputation. The publishers argued that the "serious harm" test under Section 1 of the Defamation Act 2013 required claimants to prove actual serious harm as a fact, not merely that the words had a tendency to cause it.

The Legal Question

The central question was: what does "serious harm" mean under Section 1? Two competing interpretations had emerged:

• The "tendency" test: Serious harm could be inferred from the seriousness of the defamatory imputation
• The "fact" test: Claimants must prove, as a matter of fact and with evidence, that the publication has actually caused or is likely to cause serious harm

The Supreme Court's Ruling

Lord Sumption held that Section 1 requires proof of actual serious harm as a fact. Claimants cannot simply point to the gravity of the words used — they must adduce evidence demonstrating real-world impact. Evidence can include:

• The scale of publication — how many people actually read or saw the statement
• Evidence from individuals whose opinion of the claimant changed
• Lost business, damaged relationships, social exclusion
• The inherent tendency of the words considered alongside actual circumstances

Crucially, serious harm can be proved by inference — but those inferences must be drawn from actual facts, not merely from the words themselves.

What This Means for Claimants

• Evidence gathering is critical: Collect witness statements, analytics data, and evidence of lost opportunities from the outset
• Publication scale matters: A post read by 50 people may not meet the threshold; the same words on a national website likely will
• Timing is important: Harm that develops over time counts — serious harm can be assessed at trial
• Businesses face a higher bar: Under Section 1(2), bodies trading for profit must show "serious financial loss"

Impact on Subsequent Cases

Since Lachaux, courts have accepted social media analytics, Google search data, and expert evidence on reputational damage. The test has been applied to private message cases with small audiences, often dismissing them for insufficient reach.

Practical Advice

1. Preserve all evidence — screenshots, URLs, dates, audience data
2. Document tangible harm — lost clients, cancelled contracts, social consequences
3. Keep a timeline of events flowing from the publication
4. Seek specialist legal advice to assess whether the serious harm threshold is likely to be met

Related reading: Defamation Act 2013 explained | How to prove defamation | Defamation compensation