What Does Causation Mean?

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Kate McCue

Medical Negligence Associate Solicitor

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Causation can be used in two different ways when making either a medical negligence claim or a personal injury claim. You may hear either medical causation being referred to during a medical negligence or a personal injury claim. Alternatively, you may hear causation generally or legal causation being referred to when discussing the accident circumstances in a personal injury claim. 

In a personal injury claim, legal causation is essentially the principle that in order to be successful in a claim, you must be able to prove a direct link between the accident circumstances and the negligence of a third party.  For these purposes, legal liability or liability in negligence is established when there is a breach of the duty of care owed by the defendant (for example, an employer or an occupier of a premises) to the claimant (i.e. the person who has been injured).

If this can be established, it then has to be proven that the negligence of the defendant directly caused loss, injury and damage to the claimant. This may include and be referred to as medical causation. Broadly speaking, it is not enough to simply show that you have sustained an injury following an accident as you must also show that the accident directly caused these injuries.

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Example of Medical Causation in a Personal Injury Claim

A simple example of this may be that a person is involved in a nonfault road traffic accident where they sustained muscular injuries to their neck and back. A few days following the accident, they start to notice that their ankle is slightly tender and painful to touch. They are unsure if the road traffic accident has caused this.

During the course of their personal injury claim, a medical expert is instructed to evaluate the injuries sustained as a result of the accident and the length of time these injuries either did or are expected to last for. This is a normal part of the process which allows the medical expert to establish medical causation.

In this example, the medical expert may consider the medical records of the person, examine them and take their general history before coming to the conclusion that while their other injuries were caused by the accident, the pain to the ankle was not and is simply coincidental or as a result of another factor. As such, medical causation has only been established for the muscular injuries to the persons neck and back.

Example of Medical Causation in a Medical Negligence Claim

Medical causation must be established in a medical negligence claim too and, given the nature of the case, is often the main focus of the claim. An example of this can be shown through one of our previous clients, Mr Mikombe.

Mr Mikombe was suffering from pain in the right side of his stomach. He went to a consultation with his GP who sent him for a CT scan. This scan revealed that the pain he was in was due to a 9mm kidney stone. He had a standard operation to remove the stone from his kidneys and insert a stent, which would help his kidneys work properly again. As part of a routine follow up procedure for this type of operation, Mr Mikombe should have seen a doctor one month after the operation to get the stent removed. His appointment was scheduled for five months after his operation.

One month before this follow up appointment, he was unfortunately rushed into the Accident and Emergency Department of his local hospital as he was in severe pain. He had developed a serious bladder condition because the stent they had placed  into his body had been there for too long. He had to have emergency treatment, a second stent was placed in and multiple operations were performed to rectify the problem.

This is a classic case of causation in medical negligence as by failing to arrange the follow up appointment within the standard timeframe, the hospital gave Mr Mikombe substandard medical treatment for his health problem which then caused him further and unnecessary pain and suffering.

How Do We Prove Causation in Medical Negligence Claims?

To prove causation in a medical negligence claim, our expert team of Medical Negligence Lawyers will initially carry out what’s known as the  “but for” test. This is a question that asks: “but for the existence of X, would Y have occurred?”

An example of this could be, for instance, “But for the doctor’s substandard treatment, would the patient have suffered those injuries?”. If we can answer yes to that question, we will then move on to making the c clinical negligence claim which typically has two different stages.

Stage 1: Proving a Lack of Duty of Care

The first stage of the claims process is to show that a doctor or hospital has breached their duty of care towards the patient. We assess their approach to the patient’s health condition to examine if they’ve acted in an unreasonable way. If we can prove that, then we’re halfway there with the claim.

To do this, we will refer to accepted guidelines on patient treatment and assess whether an alternative course of action would have had a better outcome. If so, we need to assess whether it would have been reasonable for the doctor or hospital to take this course of action initially or more quickly than they did.

Stage 2: Proving Patient Suffering

The second stage of making a medical negligence claim would be to show how the doctor or hospitals unreasonable approach to the patient’s health condition led to an injury, deterioration of an existing injury or condition, or failure to recover from their existing condition.

If the patient has died, then their family may be able to show that the death was caused by the negligent treatment.

Is Proving Causation In Medical Negligence Claims Difficult?

Unfortunately, causation in medical negligence claims can be difficult and can often fall into a grey area.

For instance, sometimes, a patient might have a preexisting condition that affects their medical treatment or prospects of recovery. If that’s the case, a doctor or hospitals treatment of that patient might not necessarily be the cause of any deterioration.

Essentially, we need to show what could have happened if the doctor hadn’t breached their duty of care to allow the comparison between this and what did happen to be fully seen. This will show the full impact that the medical negligence has had on you.

If we can’t show that your injuries were a direct result of a doctor or hospitals unreasonable behaviour, we wouldn’t be able to proceed with the claim.

Even if the doctor admits to a breach of duty of care, they may still argue that even with the best care, the outcome would be the same.

In these cases, further investigation would be needed. We’d review your medical records and instruct medical experts to give their opinions on the treatment you received and if it’s likely to have caused injuries that could’ve been avoided.

Is There a Time Limit for Making a Medical Negligence Claim?

You have three years from the date of injury d or the date you found out about the negligemce treatment (which is called the date of knowledge), to make a claim for medical negligence. Exceptions apply to minors and deceased. 

If you think you’ve suffered an injury or a worsening condition because a doctor or hospital gave you substandard treatment, get in touch with a Medical Negligence Solicitor as soon as you can.

How Simpson Millar Can Help You With Your Medical Negligence Claim

It’s important to get in touch with a Medical Negligence Solicitor if you believe something went wrong during your treatment or stay in hospital.

We’re specialists in this area and we have considerable experience with investigating medical negligence incidents and working with independent experts to help establish causation.

Our team of qualified Medical Negligence Solicitors will undertake all the necessary investigations for you, run your case from start to finish and arrange appointments with all of the appropriate medical specialists. This means that you don’t have to be concerned about the complexity or stress of this in addition to your ordinary caring responsibilities. Our team will regularly provide you with support and clear, straightforward information and advice throughout the whole medical negligence claims process to reassure you and guide you every step of the way.

We understand the impact that substandard medical care and making a claim for Medical Negligence can have on you: It can severely impact your life. It’s distressing, overwhelming and frustrating, so we’ll work hard to make it as easy for you as possible.

We’ll be open and honest about the entire claims process and advise you if we believe you have a good chance of making a successful Medical Negligence claim. We’ll be there, with you, throughout the entire claims process to help and support you during this difficult time. We may even be able to assist you on a No Win, No Fee basis – just ask us for further details about this.

If you are looking for a no obligation chat about a possible medical negligence claim, our friendly and dedicated team is ready and waiting to take your call on 0808 239 6043. Alternatively, you can request a call back and one of our team will contact you as soon as possible.


Simpson Millar LLP. (n.d.). Medical Negligence Solicitors. Retrieved from https://www.simpsonmillar.co.uk/medical-negligence-solicitors/ (Accessed: 31/12/2023)

Simpson Millar LLP. (n.d.). Personal Injury Solicitors. Retrieved from https://www.simpsonmillar.co.uk/personal-injury-solicitors/ (Accessed: 31/12/2023)

Simpson Millar LLP. (n.d.). No Win No Fee Personal Injury Solicitors. Retrieved from https://www.simpsonmillar.co.uk/personal-injury-solicitors/no-win-no-fee-personal-injury-solicitors/ (Accessed: 31/12/2023)

Kate McCue

Medical Negligence Associate Solicitor

Areas of Expertise:
Medical Negligence

Kate joined the Clinical Negligence department at Simpson Millar in January 2023 after previously working at Chris Kallis Solicitors in Plymouth. Kate qualified as a solicitor in 2004 and has developed extensive experience in both Personal Injury and Medical Negligence.   

Initially Kate started working as a Defendant Solicitor for firms such as Bond Pearce LLP and DAC Beachcroft Claims Ltd. This has allowed Kate to develop a tactical advantage to her cases, using the experience of how a claim is dealt with from a Defendant’s perspective. 

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