Law of Evidence – What is it?

The law of evidence encompasses the rules and legal principles that govern the proof of factual matters in both criminal and civil proceedings. It is the evidence that helps the parties prove or disprove their case and, in turn, assist the court in fairly determining the outcome of those proceedings.

Below we examine the different types of evidence that may be used in both criminal and civil proceedings, together with an overview of some of the legal principles that provide the foundations underpinning the law of evidence.

What constitutes evidence?

Under the law of evidence, there are several different types of evidence that may be used in both criminal and civil proceedings. These include:

  • oral evidence – this is the spoken testimony of a lay or expert witness given in open court, usually on oath or affirmation. For the lay witness, the evidence is limited to their own knowledge of the facts, rather than conjecture, and is put forward as the truth of its contents. The expert witness, on the other hand, may provide their professional opinion on a particular issue to assist the court in its determination of that issue.
  • written evidence – this is the written testimony of a lay witness, usually signed with a statement of truth. It can also include the written report of an expert, such as a medical, forensic or handwriting expert. Typically, oral evidence will be given to corroborate a written statement or report.
  • documentary evidence – this is any document or written record, such as a contract, letter, diary or incident report. It can also include transcripts of telephone calls, as well as digital records of communications, such as text messages or emails. Typically, documentary evidence will be exhibited to a written statement or report, either by the author of the document in question, or by an individual able to verify or explain its contents.
  • real evidence – this is tangible evidence in the form of some kind of material object. This includes DNA evidence, such as hair or blood samples, typically used in conjunction with an expert’s report. It can also include CCTV footage, still photographs, and voice or video recordings. It is produced before the court for inspection, either to prove that it exists, or so that the court can draw an inference as to its condition or value.

The legal principles of the law of evidence

In any legal proceedings, both criminal and civil, the parties must produce evidence in support of their case to prove or disprove the matters in dispute. Accordingly, in the absence of sufficient evidence their case is likely to fail.

However, there are various rules and legal principles within the law of evidence that govern, for example, which party bears the burden of proof and to what standard. There are also rules as to the admissibility and weight to be attached to the evidence. Below, we address each of these legal principles in turn.

Burden of proof 

The burden of proof refers to the obligation placed upon a party to prove or disprove a disputed matter. Generally speaking, the burden of proof lies with the party bringing the action. For example, in criminal proceedings, the duty is on the prosecution to prove the elements of any offence. In a civil case, it is typically the claimant who is charged with the burden of proving his/her claim.

The burden of proof may shift, however, depending on the particular defence raised. By way of example, the onus in proving a plea of insanity rests with the defendant charged with a criminal offence. In a civil context, the evidential burden, at the very least, may shift to the defendant when pleading and proving an allegation of fraud.

Standard of proof

The standard of proof refers to the strength of the evidence required to prove a disputed fact or issue. In a criminal trial, the prosecution must prove the elements of any offence “beyond a reasonable doubt”, ie; so that the jury is sure of the defendant’s guilt. In contrast, a claimant bringing a civil claim must only prove their case on a “balance of probabilities”, ie; so that the judge is satisfied that the matters in dispute are more likely than not.

In a criminal context, the higher standard of proof leans very much in favour of the defendant. Given the serious nature of any criminal conviction, it is deemed preferable that some guilty go free, rather than any innocents be convicted. Similarly in civil cases, the more serious the allegation, the stronger and more cogent the evidence should be before a court determines that, on the balance of probabilities, the matters in dispute are proven.

Admissibility of evidence

In both criminal and civil proceedings, under the law of evidence any statement, testimony, document, or other evidence that is relevant to an issue in dispute, is potentially admissible. This includes issues of fact, as well as any issues that may affect the reliability or credibility of a witness or the evidence.

However, the question of admissibility of evidence is also subject to any common law or statutory rules on exclusion. By way of example, evidence may be wholly excluded in criminal proceedings if it has been obtained illegally, improperly or unfairly, such as during an unlawful police search.

In criminal proceedings there are also special rules under the law of evidence relating to the admissibility of confessions, evidence of the defendant’s bad character and hearsay evidence (as defined below). This type of evidence can have an adverse effect on the fairness of proceedings such that, in many cases, it ought not to be admitted. In circumstances where such evidence is not ruled inadmissible, various procedural requirements will need to be satisfied as a means of redressing any imbalance.

Weight of evidence

Under the law of evidence, once a statement, testimony, document or other piece of evidence has been admitted, the court must then determine its’ probative value in determining the issues in dispute. Accordingly, the court will take into account a number of factors. These include the nature of the evidence and whether it can be corroborated, from where the evidence originates, and how credible and reliable that source can be regarded.

In both criminal and civil proceedings, hearsay evidence is typically regarded as inherently unreliable because it is evidence not given under oath and without any opportunity for this evidence to be tested under cross-examination. Hearsay evidence is where a witness in proceedings seeks to give evidence of a particular fact on the basis of what was said to him or her by a third party. Accordingly, very little weight will be attached to this type of evidence in determining whether the requisite standard of proof has been satisfied. 

Similarly, in the absence of direct or corroborative evidence, the court is unlikely to attach any weight to circumstantial evidence. This is evidence that tends to prove a factual matter by proving other events or circumstances from which the occurrence of the matter can be reasonably inferred.

For an in-depth look at the law of evidence 

The law of evidence is a highly complex and constantly evolving area of law. This article provides only an overview of some of the legal principles encompassed by the law of evidence in the context of both criminal and civil proceedings.  For more detailed guidance, students should refer to specific texts or analysis on the subject, with reference to current statutory provisions and recent case law. 

Legal disclaimer

The matters contained in this article are intended to be for information purposes only. This article does not constitute legal advice and should not be treated as such. Whilst every effort is made to ensure that the information is correct, no warranty, express or implied, is given as to its accuracy and no liability is accepted for any error or omission. Before acting on any of the information contained herein, expert legal advice should be sought. 

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