What Does a Forensic Accountant Do?
Key Takeaways
- Automatism is about involuntary conduct/total loss of conscious control, not simply ‘I can’t remember’ or ‘I wasn’t myself’.
- Courts distinguish non-insane (external cause) automatism (can lead to acquittal) from insane automatism (internal cause/disease of the mind) (may lead to a special verdict and orders).
- The court will scrutinise control vs impairment, cause (internal vs external), and whether the episode was foreseeable, avoidable, or self-induced.
- Winning cases are evidence-led: tight timelines, contemporaneous medical records, and objective footage/data (CCTV, phone/vehicle data) often decide outcomes.
- Expert selection is critical—neurology for seizures/head injury/sleep disorders, psychiatry for mental state/differential diagnosis, psychology for cognition/behaviour where relevant.
- Reports must answer the legal questions clearly, address alternatives/limitations, and avoid overreach—courts are alert to unsupported assertions.
The Automatism Defence
The automatism defence is one of the most misunderstood issues in criminal law. It is often spoken about as if it simply means “I do not remember”, or “I was not myself”. In reality, courts apply a strict approach: automatism is about involuntary conduct, where a person’s consciousness is so impaired that they have lost the ability to consciously control their actions.
That strictness exists for a reason. If accepted, automatism can be a complete defence and lead to an acquittal. But courts also have public protection concerns, particularly where the cause is internal and may recur. The law, therefore, draws a sharp line between non-insane (sane) automatism and insane automatism (which is treated as “insanity” in legal terms).
For reference, here is official guidance from the Crown Prosecution Service:
Crown Prosecution Service
– Mental Health: Suspects and Defendants: principles relevant to the decision to prosecute
In this specialist guide, our Forensic Defence experts provide a clear automatism definition, answer the question of what is automatism, explain what tests that courts apply, and outline the types of evidence and expert input that usually determines whether the issue is left to a jury.
Automatism Definition: What is Automatism in Criminal Law?
According to the Crown Prosecution Service, in UK criminal law, automatism is a common law defence. It applies where a person’s consciousness was so impaired that they were acting in a state of physical involuntariness, and had lost the ability to consciously control their actions, meaning they cannot be held culpable for what followed.
A few key points to take note of:
- Automatism is not just “reduced awareness” or “acting out of character”.
- It is not simply a lack of intent (mens rea). It is about whether the act was voluntary at all.
- The court will look for evidence that control was totally lost, rather than merely impaired.
In practice, judges will expect the defence to point to a recognisable mechanism for the alleged involuntary state, and in most cases, that means credible medical or scientific evidence.
The Automatism Defence Split: Why “Insane” vs “Non-insane” Matters
Courts generally recognise two types of automatism, and choosing the correct legal route is crucial:
Insane automatism (internal cause)
“Insane automatism” results from an internal cause or disease of the mind. In the Crown Court, if established, it leads to a special verdict of not guilty by reason of insanity (a legal term, not a medical label).
The CPS guidance gives examples that have been treated as internal causes, including epilepsy, hyperglycaemia due to not taking insulin, sleepwalking (in some circumstances), and arteriosclerosis.
Non-insane (sane) automatism (external factor)
Non-insane automatism results from external factors leading to loss of control, and it is a complete defence resulting in acquittal.
Examples cited in CPS guidance include a reflex reaction to being attacked by a swarm of bees, a concussion from a blow to the head, and an insulin injection (hypoglycaemia in the Quick scenario).
What Courts Typically Look for In An Automatism Defence
Although the medical backdrop can be complex, courts tend to come back to a consistent set of legal questions.
1) Was there a total loss of voluntary control, or only impairment?
A central battleground is whether the defendant’s control was totally lost.
Prosecutors will scrutinise whether control was merely impaired, rather than absent.
Practically, this often turns on:
- How purposeful the behaviour appeared.
- Whether the person responded to external stimuli.
- Whether they could navigate obstacles, speak coherently, drive, or follow a sequence of actions.
- How quickly they “came round” and what they did immediately after.
2) What caused the state: internal disease of the mind or external factor?
The court will consider whether the state arose from:
An internal cause (pushing the analysis toward insanity / special verdict)
or
An external factor (supporting non-insane automatism and acquittal).
This is not a purely medical question. A clinician may describe a condition in clinical terms, but the court applies a legal classification.
3) Was the condition foreseeable, avoidable, or self-induced?
Even where an external factor is alleged, courts will examine whether:
- The defendant could have reasonably foreseen the condition.
- There were warning signs of onset.
- Anything could have been done to avoid it.
- It was self-induced (including issues around intoxication).
These points are especially relevant in cases involving:
- Failure to manage a known medical condition.
- Medication non-compliance.
- Alcohol or drug involvement.
- Fatigue, sleep deprivation, or long-distance driving scenarios.
4) Is there a proper evidential foundation to leave automatism to the jury?
Before a jury decides anything, the judge must be satisfied there is a proper evidential foundation for the defence to be left. The CPS guidance notes that this is likely to involve the defence adducing expert evidence, and highlights judicial caution about lay decision-making without medical or scientific assistance.
Common Automatism Scenarios in UK Criminal Cases
Every case turns on its facts, but the same medical categories come up again and again.
Hypoglycaemia and diabetes-related episodes
One of the best-known examples is hypoglycaemia (low blood sugar), often linked to insulin use. In R v Quick, the Court of Appeal considered the distinction between a malfunction caused by an external factor (insulin and related circumstances) versus an internal disease of the mind classification, and held that the automatism issue should have been left to the jury on the evidence.
Courts will usually focus on:
- Insulin dosage, meal timings, and warning symptoms.
- Whether the episode was foreseeable.
- Whether steps were taken to prevent it (food, glucose, monitoring).
- The presence of alcohol (which can complicate causation).
Hyperglycaemia (high blood sugar) and internal cause arguments
The CPS guidance specifically gives hyperglycaemia due to not taking insulin as an example, treated as an insane automatism/insanity route.
Epilepsy and seizure-related behaviour
Epilepsy is also listed by the CPS as an example where the law has treated the condition as an internal cause, potentially leading to the insanity framework rather than non-insane automatism.
In practice, evidential focus will include:
- Seizure history and diagnosis.
- EEG/neurology records.
- Medication regimen and compliance.
- Witness descriptions of aura, collapse, post-ictal confusion, automatisms.
- Whether the alleged conduct aligns with known seizure patterns.
Sleep disorders: sleepwalking and sexsomnia
Sleepwalking is frequently raised, and the CPS guidance notes that sleepwalking may occur from internal or external causes, and that it has been raised in sexual offence cases (sometimes described as “sexsomnia”).
These cases are heavily evidence-led. Courts will typically look for:
- Prior sleep disorder history (or lack of it).
- Precipitating factors (sleep deprivation, alcohol, stress, medication).
- Corroboration from partners/family.
- Specialist sleep medicine input where appropriate.
Head injury, concussion, and acute external trauma
External trauma, such as a blow to the head causing concussion, is a classic non-insane automatism pathway.
Typical evidence includes:
- Ambulance and A&E notes.
- Neurological symptoms were documented in close time.
- Contemporaneous witness accounts (dazed state, confusion, collapse).
- CCTV/body-worn footage showing mechanism and onset.
Dissociation, acute stress reactions, and psychiatric considerations
Some cases are framed around dissociation or extreme psychological response. These can be difficult because courts will still require the legal ingredients: involuntary action and a properly evidenced mechanism. The key is to align psychiatric and psychological evidence with the legal questions (control, consciousness, causation, foreseeability), rather than relying on labels.
Evidence That Usually Decides Automatism Cases
The strongest automatism arguments are the ones where the timeline and the science match.
1) A tight chronology
Courts respond well to a clear, timestamped narrative:
- Preceding events (sleep, food, alcohol, medication, stressors).
- Onset indicators (odd speech, vacant staring, unresponsiveness, collapse).
- The incident itself (what was done and how it appeared).
- Recovery phase (confusion, amnesia, immediate actions, remorse, seeking help).
2) Contemporaneous medical records
A common weakness is reliance on later recollection rather than records created at the time.
Useful sources include:
- Ambulance records.
- Custody medical notes.
- A&E assessment and blood results.
- GP and specialist records showing history and recurrence risk.
3) Expert evidence (and choosing the right discipline)
Automatism often requires more than one expert lens:
- Neurology: epilepsy, seizures, head injury, altered states, and sleep disorders in some cases.
- Psychiatry: mental state at the time, dissociation, differential diagnosis, medication effects, risk and recurrence framing.
- Psychology: cognitive functioning, trauma response, suggestibility, behavioural analysis, capacity-related themes where relevant
What matters is not the label, but whether the expert can answer the legal questions with a clear methodology and properly referenced materials.
4) Objective scene evidence: CCTV, phone data, vehicle data
Automatism arguments often rise or fall on what independent evidence shows about control and responsiveness.
CCTV can be crucial for:
- Gait, balance, and apparent awareness.
- Response to voices or obstacles.
- Purposeful sequences (entering, selecting items, leaving).
- Collapse or recovery markers.
If CCTV is important to your case strategy, enhancement and clarification can assist with usability and presentation:
5) Toxicology and alcohol: separating intoxication from automatism
Where drink or drugs are in play, courts will scrutinise causation and self-induction. The CPS guidance highlights self-induced intoxication as a key scrutiny point (and notes legal complexity around some aspects).
In driving cases, evidential interpretation can also depend on clear calculations and assumptions. If alcohol levels, timing, and back calculation are disputed, specialist support can be relevant:
How Automatism is Presented in Court: Reports, Standards, and Scrutiny
Courts expect expert evidence to be transparent, reasoned, and properly limited to the expert’s field. The Criminal Practice Directions emphasise the court’s role in assessing admissibility and weight of expert evidence, and states a requirement for an expert report under the Criminal Procedure Rules.
Courts and Tribunals Judiciary
In practical terms, a strong expert report in an automatism case will usually:
- Set out the materials reviewed (statements, records, CCTV, test results).
- Explain the diagnostic framework used (and why).
- Address differential diagnoses (including malingering, intoxication, mental illness, ordinary anger).
- Link opinion to evidence, not assertion.
- Deal directly with the legal questions: control, consciousness, causation, foreseeability, recurrence risk (where relevant).
- State limitations clearly.
Courts are alert to overreach. A report that strays into advocacy, ignores contrary evidence, or relies on assumptions without support will usually be less persuasive.
If the Defence Succeeds: Acquittal vs Special Verdict and What Happens Next
Outcomes depend on whether the case is treated as non-insane automatism or insane automatism.
Non-insane automatism
If accepted, the defendant is acquitted because the conduct is treated as involuntary.
Insane automatism (special verdict)
In the Crown Court, successful insane automatism results in a special verdict of not guilty by reason of insanity.
Following a special verdict, the court must make one of a limited range of orders (hospital order with or without restriction, supervision order, or absolute discharge), as reflected in CPS guidance and the statutory framework.
This is one reason why correctly classifying the defence route matters so much: the consequences can be very different from an unqualified acquittal.
A Practical Checklist for Solicitors: Building an Automatism-ready Instruction
If you are considering an automatism defence, the earliest steps often shape the eventual outcome.
- Lock down the timeline (sleep, meals, medication, alcohol, triggers, onset, recovery).
- Secure contemporaneous records (ambulance, custody healthcare, A&E, bloods).
- Preserve objective evidence (CCTV requests early, phone data, vehicle/telematics if relevant).
- Identify the correct expert discipline (neurology vs psychiatry vs psychology, or more than one).
- Frame instructions around legal questions (control, consciousness, causation, foreseeability, recurrence).
Plan for challenge: anticipate prosecution scrutiny on impairment vs total loss, avoidability, and self-induction.
Relevant Expert Witness Services for Automatism Cases
Automatism cases are rarely “one report and done”. They often involve medical causation, behavioural interpretation, and high scrutiny of objective evidence.
Forensic Defence’s wider expert witness service categories can be viewed here.
Depending on the case theory, the following are commonly relevant:
CCTV enhancement
(where footage is central)
Drink drive BAC calculation
(where alcohol timing/levels are disputed)
The right approach is to match the expert to the mechanism alleged, and to ensure the report answers the court’s real concerns: what caused the state, how it affected control, whether it was foreseeable/avoidable, and what the evidence shows.
Automatism FAQs
Is “I cannot remember” enough for automatism?
No. Memory loss can occur for many reasons. Automatism requires evidence of a state of physical involuntariness and loss of conscious control, not simply amnesia.
Can sleepwalking be non-insane automatism?
Sometimes it may be argued to arise from external causes, but it is heavily fact-dependent. The CPS guidance recognises sleepwalking may occur from external causes and notes it has featured in some sexual offence defences.
Does the defence need expert evidence?
Often, yes. The CPS guidance notes that the judge must decide if there is a proper evidential foundation before leaving automatism to the jury, and that this is likely to involve expert evidence.
What happens if the court treats it as insane automatism?
In the Crown Court, it can lead to a special verdict, and the court then has a limited range of orders available, set out in statute and reflected in CPS guidance.
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