What Is a Medico-Legal Causation Analysis?

In clinical negligence and personal injury litigation, establishing that something went wrong is only half the battle. To succeed in law, it isn’t enough to prove that a clinician breached their duty of care, you must also show that this failing caused harm. This critical link is where a medico-legal causation analysis comes in.

A causation analysis, sometimes referred to as a causation report, is a detailed, expert-led assessment that bridges the gap between breach and outcome. It answers the question that often defines the success or failure of a case:

“Would the claimant’s outcome have been different, but for the breach of duty?”

What Is a Medico-Legal Causation Analysis Report?

A medico-legal causation report is an independent expert opinion that determines whether a proven breach of duty caused, materially contributed to, or had no bearing on a claimant’s outcome. It combines medical knowledge, clinical evidence, and legal principles to draw a clear, reasoned conclusion.

The report provides the court and legal teams with an evidence-based foundation for establishing causation, one of the three pillars of negligence alongside duty and breach.

Without it, even the most compelling case on liability can fail.

When Is a Causation Report Needed?

A causation report is typically requested once liability has been established, that is, when it has been accepted or found that care fell below a reasonable standard. However, not every breach results in damage. A missed diagnosis may not have changed the clinical outcome, or a delay in treatment may have had no measurable effect on recovery.

Instructing a causation report becomes essential when:

• Multiple potential causes of harm exist (e.g., complex medical conditions, co-morbidities, or delayed interventions).

• There is a significant time gap between the negligent act and the injury.

• It is uncertain whether earlier or different care would have altered the patient’s outcome.

In short, causation analysis brings clarity to cases where the clinical pathway is complex or disputed.

What Does a Causation Expert Do?

The expert reviewing a case performs a meticulous, structured evaluation of all available evidence - medical records, witness statements, diagnostic results, and medical chronologies. Their primary task is to answer a single legal question:

“On the balance of probabilities, would the claimant have avoided the harm if the breach had not occurred?”

To do so, they apply the principles established by key cases such as:

• Bolam v Friern Hospital Management Committee (1957) – establishing the standard of care.

• Bolitho v City and Hackney Health Authority (1997) – confirming that expert opinions must withstand logical scrutiny.

• Montgomery v Lanarkshire Health Board (2015) – defining patient-centred consent and disclosure.

By applying these principles, the expert assesses whether the harm was inevitable,

avoidable, or partially contributed to by substandard care.

The Analytical Process

Causation analysis involves both clinical insight and logical reasoning. Experts typically work through the following steps:

1. Reviewing the evidence – assessing all relevant medical records, statements, and imaging.

2. Constructing a timeline – identifying when key decisions, omissions, or delays occurred.

3. Considering alternative scenarios – comparing what actually happened with what would have occurred had care been appropriate.

4. Evaluating outcome differences – determining whether earlier or proper intervention would have prevented or lessened harm.

5. Formulating an opinion – setting out, with reasoning, whether causation is established, partial, or absent.

The final report is clear, reasoned, and transparent. It avoids speculation, instead focusing on what can be supported by evidence and established medical fact.

Who Provides the Causation Opinion?

Causation reports are written by clinical experts with specialist knowledge relevant to the case - surgeons, physicians, nurses, or other healthcare professionals actively practising in their fields.

At Apex Experts, our panel comprises experienced clinicians who:

• Maintain registration with their regulatory bodies (e.g., GMC, NMC).

• Hold extensive experience in both clinical practice and medico-legal reporting.

• Work independently of the instructing party to ensure impartiality.

• Are trained to produce CPR Part 35-compliant reports that meet the court’s standards for expert evidence.

Each expert is supported by our dedicated administration team, ensuring efficient turnaround and robust quality control.

How Long Does It Take?

Timeframes vary depending on case complexity, record volume, and the number of issues to be addressed. However, a standard causation report can typically be delivered within 6–8 weeks of instruction, provided all documentation is complete.

Complex, multi-cause cases may take longer, particularly where multiple experts across disciplines are involved (for example, obstetric, neurological, and neonatal specialists in a birth injury claim).

Legal and Clinical Value of Causation Reports

A medico-legal causation analysis serves several vital purposes in litigation:

1. Establishing the Link Between Breach and Harm

It determines whether substandard care caused the injury—or whether the outcome was inevitable despite it.

2. Informing Settlement Strategy

Causation reports often guide early settlement discussions or mediation, helping parties understand the strength of their case.

3. Clarifying Complex Medical Evidence

They translate intricate clinical issues into structured, logical reasoning that judges and legal professionals can understand.

4. Supporting Expert Collaboration

When multiple experts contribute to a case, causation reports form the foundation for consistent analysis and joint statements.

5. Promoting Fairness

By grounding legal arguments in medical reality, causation analysis ensures compensation decisions are based on evidence rather than assumption.

Causation in Practice: Common Scenarios

Medico-legal causation analyses are used across a wide range of case types, including:

• Delayed diagnosis or treatment (e.g., sepsis, cancer, stroke).

• Birth injury claims (assessing whether earlier intervention would have changed neonatal outcomes).

• Surgical errors (evaluating whether harm resulted from technique or pre-existing pathology).

• Medication errors (considering whether incorrect prescriptions or missed doses caused deterioration).

• Falls or pressure ulcers (assessing preventability and timelines).

In each, the question remains the same: did the breach make a meaningful difference to the outcome?

The Role of Causation in the Legal “Three-Part Test”

Negligence in law has three components:

1. Duty of care – owed by the clinician to the patient.

2. Breach of duty – failure to meet a reasonable standard of care.

3. Causation – proof that this breach caused harm.

Even where duty and breach are proven, without causation the claim cannot succeed. This makes the causation report one of the most decisive pieces of evidence in clinical negligence proceedings.

Final Thoughts: Why Causation Reports Matter

In clinical negligence cases, breach alone is never enough. Without causation, there is no compensation. A medico-legal causation analysis provides the crucial bridge between what went wrong and what that meant for the patient.

By combining clinical expertise with legal understanding, causation reports ensure that decisions are based on evidence, not conjecture. They give clarity to courts, confidence to solicitors, and closure to patients.

At Apex Experts, our panel of specialists provides clear, impartial, and fully reasoned medico-legal causation reports across all areas of healthcare. Whether you’re assessing liability, preparing for settlement, or building your expert evidence base, our team can help ensure that your case stands on solid, evidence-based ground.