The rules about who must prove what, and to what standard, are fundamental to a fair criminal justice system. They protect defendants from being convicted without sufficient evidence. If you understand these rules, you can identify when the prosecution has not met its obligations and when a statutory provision might shift the burden onto your client.
There are always two questions to ask: (1) who bears the burden of proof on a particular issue, and (2) what is the standard of proof required? The burden can rest on the prosecution, the defence, or sometimes be shared. The standard can be "beyond reasonable doubt" or "on the balance of probabilities". Getting these right is essential.
This is the most important case on burden of proof in criminal law. The House of Lords established what Viscount Sankey LC called the "golden thread" of English criminal law: throughout the web of the criminal law, you will find the principle that the prosecution must prove the defendant's guilt. This principle applies to all criminal cases unless Parliament has expressly or impliedly provided otherwise.
Woolmington shot and killed his wife. He claimed the gun went off accidentally. The trial judge directed the jury that once the prosecution proved the killing, the burden shifted to the defendant to prove it was an accident. The Court of Criminal Appeal upheld the conviction, but the House of Lords reversed it, holding that the trial judge's direction was wrong. The prosecution must prove every element of the offence.
Viscount Sankey LC: "Throughout the web of the criminal law one golden thread is always to be seen, that it is the duty of the prosecution to prove the prisoner's guilt subject to what I have already said as to the defence of insanity and subject also to any statutory exception."
Think of Woolmington as the default rule: the prosecution always bears the burden of proving every element of the offence. Only specific statutes or established common law exceptions can shift this burden. When you encounter a new offence, ask yourself: is this a straightforward application of Woolmington, or does a statute shift the burden?
The golden thread is subject to exceptions. Viscount Sankey himself recognised two: the defence of insanity, and statutory exceptions. Parliament has since created many statutory reverse burden provisions. These exceptions must be interpreted narrowly - the court will presume that Parliament did not intend to reverse the burden unless the statutory language clearly requires it.
The legal burden (also called the persuasive burden) is the obligation to prove a fact on the balance of probabilities. If a party bears the legal burden and fails to discharge it, they lose on that issue. In criminal cases, the legal burden normally rests on the prosecution throughout, but it can be placed on the defence by statute. When the defence bears the legal burden, they must prove the defence on the balance of probabilities.
The evidential burden is the obligation to adduce sufficient evidence to raise an issue that the jury (or magistrates) must consider. It is a lower threshold than the legal burden. You just need to put enough evidence before the court to make the issue a live one. If you satisfy the evidential burden, the legal burden remains on the prosecution to disprove the issue beyond reasonable doubt.
| Feature | Legal Burden | Evidential Burden |
|---|---|---|
| Also called | Persuasive burden | Discharge burden / evidential burden |
| Who normally bears it | Prosecution | Defence |
| Standard required | Balance of probabilities | Enough to raise a live issue |
| What if discharged | Issue decided in your favour | Issue left for jury to decide |
| What if not discharged | Issue decided against you | Issue does not go to the jury |
| Consequence of failure | Conviction or loss of defence | Judge can withdraw issue from jury |
| Shifted by statute? | Only with clear words | More easily imposed |
Think of it this way: the evidential burden just gets your foot in the door. If you raise enough evidence on, say, self-defence, the prosecution must then disprove self-defence beyond reasonable doubt. But if the statute puts the legal burden on you, you must prove self-defence on the balance of probabilities. The difference is enormous for your client.
This is the standard required of the prosecution in criminal cases. The jury must be sure of the defendant's guilt before they can convict. The phrase "beyond reasonable doubt" is the traditional expression, but judges sometimes tell juries they must be "sure" - which is considered a more helpful formulation. It is a high standard, reflecting the seriousness of a criminal conviction.
This is the civil standard: more likely than not, or above 50%. It applies when the defence bears the legal burden of proving a defence (e.g. insanity, statutory defences). It is a significantly lower standard than beyond reasonable doubt. The defendant does not need to prove their defence to any high degree of certainty, just that it is more likely than not.
The Judicial Studies Board recommends that judges tell juries they must be "sure" of guilt rather than using the traditional phrase "beyond reasonable doubt". This is because "beyond reasonable doubt" can confuse juries into thinking they need to eliminate every conceivable doubt, no matter how fanciful. "Sure" captures the right level: a high degree of certainty, but not absolute certainty.
Parliament sometimes passes laws that place the legal burden of proving a fact on the defence, rather than the prosecution. These are called "reverse burden" provisions. They can require the defendant to prove a defence on the balance of probabilities. Because they reverse the golden thread, courts interpret them strictly and only impose the legal burden where the statutory language clearly requires it.
The defence of insanity is the classic example of a reverse burden. Under the M'Naghten Rules, once the defendant raises evidence of insanity, the defence bears the legal burden of proving it on the balance of probabilities. This was recognised by Viscount Sankey in Woolmington as one of the two established exceptions to the golden thread. The prosecution does not have to disprove insanity - the defence must prove it.
Diminished responsibility under s.2 Homicide Act 1957 also places the legal burden on the defence. The defendant must prove on the balance of probabilities that they were suffering from an abnormality of mental functioning which substantially impaired their ability to do one or more of the things mentioned in s.2(1). This was confirmed in R v Golds [2016] UKSC 61.
When advising a client, you need to know whether the burden is legal or evidential. If the defence bears the legal burden and fails to discharge it, the defence is not available. This can make the difference between a conviction for murder (with a mandatory life sentence) and a conviction for manslaughter. Always check the statute carefully.
Under the Misuse of Drugs Act 1971, it is an offence to possess a controlled drug. The prosecution must prove possession and knowledge or suspicion that the substance is controlled. However, for offences under s.5(3) (possession of a controlled drug in a premises), the occupier or person concerned in the management of the premises bears the burden of proving they neither knew nor had reason to suspect the offence was taking place.
Under s.1 Prevention of Crime Act 1953, it is an offence to have an offensive weapon in a public place. The prosecution must prove possession in a public place. The defendant bears the legal burden of proving a lawful authority or reasonable excuse under s.1(4). This means if the defendant claims they had the weapon for a legitimate purpose, they must prove this on the balance of probabilities.
Under s.1 Sexual Offences Act 2003, the prosecution must prove that the defendant did not reasonably believe the complainant consented. However, the defendant bears the evidential burden of raising the issue of belief in consent. This means the defendant must adduce sufficient evidence that they held a reasonable belief in consent for the issue to go to the jury.
When faced with a statute, look for the specific language. If the statute says "it is a defence to prove that X", the legal burden is on the defence. If it says "if the defendant raises evidence that X, the prosecution must disprove it", only the evidential burden is on the defence. The precise wording matters enormously.
A presumption is a legal rule that requires a court to assume a particular fact unless evidence is produced to rebut it. In criminal law, presumptions can affect both the burden and standard of proof. Some presumptions are rebuttable (can be disproved by evidence), while others are irrebuttable (cannot be disproved regardless of the evidence).
The presumption of innocence is the most fundamental presumption in criminal law. It means that a defendant is presumed innocent until proven guilty. This is enshrined in Article 6(2) ECHR and is the foundation of the golden thread. The prosecution must displace this presumption by proving guilt beyond reasonable doubt. The defendant does not have to prove their innocence.
Rebuttable presumptions shift the burden of proof to the defendant to disprove the presumed fact. For example, under s.75 Road Traffic Act 1988, there is a presumption that a blood alcohol reading taken within the specified time is accurate. The defendant can rebut this presumption by showing the test was unreliable. The defendant bears the evidential burden of raising the issue.
Irrebuttable presumptions (where a fact must be taken as proved regardless of evidence) are highly problematic under Article 6(2) ECHR. The European Court of Human Rights has consistently held that irrebuttable presumptions of fact that remove the prosecution's obligation to prove guilt violate the presumption of innocence. The UK courts follow this approach.
Everyone charged with a criminal offence shall be presumed innocent until proved guilty according to law. This is the European Convention on Human Rights provision that protects the presumption of innocence and places the burden of proof on the prosecution.
Article 6(2) ECHR requires courts to assess whether reverse burden provisions are compatible with the presumption of innocence. The key question is whether the provision only requires the defendant to raise an issue (evidential burden) or whether it requires them to prove a fact (legal burden). If a provision imposes a legal burden on the defendant and the fact is an essential element of the offence, it may violate Article 6(2).
In Lambert, the House of Lords held that a reverse burden provision under the Misuse of Drugs Act 1971 (requiring the defendant to prove they did not know the substance was controlled) was compatible with Article 6(2) only if read as imposing an evidential burden, not a legal burden. The House of Lords used s.3 HRA 1998 to read down the provision to preserve its compatibility with the Convention. This was a landmark decision on the relationship between reverse burdens and human rights.
In Johnstone, the House of Lords refined the approach. The court distinguished between reverse burdens that relate to elements of the offence (which are more likely to violate Article 6(2)) and reverse burdens that relate to exceptions or defences (which are less problematic). The court accepted that Parliament can impose legal burdens on defences, provided this is proportionate and necessary.
When assessing whether a reverse burden is compatible with Article 6(2), courts apply a proportionality test. They consider: (1) what the provision aims to achieve, (2) the importance of what the defendant must prove, (3) the difficulty the defendant may face in proving it, and (4) the seriousness of the offence. If the provision is proportionate, it may survive Article 6(2) challenge even if it imposes a legal burden.
When advising a client, you need to identify: what elements the prosecution must prove, whether any element is subject to a reverse burden, what defences are available and who bears the burden for each, and the standard of proof that applies. This analysis shapes your entire defence strategy, from what evidence to gather to what arguments to advance at trial.
If the defence bears the evidential burden, your strategy is to put just enough evidence before the court to raise the issue. This might be through cross-examination, defence evidence, or submissions of no case to answer. If the defence bears the legal burden, you need to actively prove the defence on the balance of probabilities, which requires stronger evidence and potentially calling witnesses.
If the prosecution has failed to discharge the burden of proof on any essential element of the offence, you can make a submission of no case to answer. Under R v Galbraith [1981] 1 WLR 1039, a judge should uphold the submission if there is no evidence that the jury could properly find the defendant guilty, or if the evidence is so weak that a conviction would be unsafe. This is a powerful tool - use it when the prosecution case is genuinely deficient.
Before trial, write out every element of the offence and note who bears the burden for each element and what the standard is. This checklist is your roadmap for trial preparation. It tells you exactly what the prosecution must prove and where you need to focus your defence evidence.
If your client faces a reverse burden, you need to prepare evidence to discharge it early. Do not wait until trial. If the defence bears the legal burden on a key issue, failing to discharge it can result in a conviction even if the prosecution evidence is weak. Prepare your evidence with the same rigour you would expect from the prosecution.