Law Matters


Providing Forensic / Expert Evidence.

Any forensic expert can increase their professional contribution to the UK criminal (and civil) justice systems by ensuring they have a clear and up to date grasp of what the law requires of them.

Simply summarised, the application of law must be:

  • Consistent: local & national, public & private;
  • Clear: reports and statements;
  • Compliant: with Criminal Procedure Rules;
  • Cost efficient: proportionate to the issues in each case;
  • Collaborative: understanding partnership roles;
  • Communicative: avoid ‘silos’;

Quality: Regulatory & professional standards.

In criminal cases in England and Wales, the Crown Prosecution Service (CPS) essential elements are;

  1. Applicable statute and case law in the jurisdiction of England & Wales;
  2. The Code for Crown Prosecutors (8th edition, 26/10/2018 );
  3. The Criminal Procedure Rules;
  4. The Criminal Procedure and Investigations Act, 1996;
  5. Effective Forensic Case Management and proportionate prosecutions;
  6. The absence of a contractual relationship between FSPs and end-users, namely the CPS and the courts (Ministry of Justice [MoJ] );
  7. The CPS Core Quality Standards.

The Code for Crown Prosecutors:

All Crown Prosecutors in England and Wales (along with a number of other prosecuting authorities) must apply this when considering every prosecution throughout the life of any case.

Application of the Code has two stages:

  • The Evidential Stage, and
  • The Public Interest Stage

The Evidential stage must be satisfied before the Public Interest stage can be considered.

The Evidential Stage requires that there is sufficient evidence to make a conviction more likely than not:

To evaluate strength of Forensic Evidence, prosecutor must be satisfied that it is:

  • Relevant
  • Reliable
  • Credible
  • Admissible

The Public Interest stage requires evaluation of whether, having satisfied the evidential stage, it is in the public interest to continue with the prosecution.

Forensic professionals must consider how prosecutors will achieve that across the range of forensic scientific and medical evidence, when preparing reports.

The Role of the Experts:

Whilst it is for the jury to evaluate expert evidence presented to it, the evaluation of the expert him/herself should clearly precede this.

"Judges should be proactive in exercising their duty to establish the expertise of witnesses appearing before them and should ensure that courts are not used to push a theory with an insufficient scientific base. Judges should also ensure that experts have recent clinical experience...“    

(The Kennedy Report (2004) "Sudden Unexpected Death in Infancy: A multi-agency protocol for care and investigation - The report of a working group convened by The Royal College of Pathologists and The Royal College of Paediatrics and Child Health")

The basics of the Criminal Procedure Rules: Managing Expert Evidence & Expert Witnesses.

“Where there is a difference of opinion between experts for the Prosecution and the Defence, it is vital that all expert reports are disclosed well before a trial commences” (Criminal Procedure Rules, Rule 19 ,2017)

Pre-trial Case Management:

Strict adherence to, and implementation of, the regime provided by the Criminal Procedure Rules will facilitate clear steps being taken in the service, consideration and agreement (or otherwise) of expert opinions.

The primary purpose of robust pre-trial management is to narrow down the real issues, particularly those of a scientific nature, which the jury must decide upon.

The Criminal Procedure Rules (CrPR) were originally issued in 2005 following the then Attorney General’s review into Shaken Baby Syndrome deaths and other miscarriages of justice.

They apply to all participants throughout the conduct of a criminal case. Of particular relevance are:

Part 1: The Overriding Objective

Part 3: Identification of issues

Part 19: Expert Witnesses & Expert Evidence

Parts 21 & Disclosure (+ Unused per CPIA)

Criminal Procedure Rules (CrPR), Rules 1, 3 and 19:

Rule 1: The ‘Overriding Objective’ is that criminal cases must be dealt with justly;

Rule 3: ALL participants (includes experts for prosecution and defence) must assist with the ‘Overriding Objective’;

R 3.2.a Parties’ duty is early identification of issues + agreement

Trial only on live issues

Outgoing SPJ (Leveson) directive issued 12/2009

applying R3 is “compulsory”.. ‘must’ means MUST

Rule 19: Expert Evidence;

R 19.2; Duty to the Court (Inc. compliance, deadlines etc.)

R 19.3; Contents of Report; accreditation, area of expertise

where there is a range of opinion on the matters dealt with in the report:

Identify issues and areas of agreement;

R 19.6; pre-hearing discussion of expert evidence


Pre-hearing discussion of expert evidence

19.6. (1) This rule applies where more than one party wants to introduce expert evidence.

(2) The court may direct the experts to—

  1. discuss the expert issues in the proceedings; and
  2. prepare a statement for the court of the matters on which they agree and disagree, giving their reasons.

(3) Except for that statement, the content of that discussion must not be referred to without the court’s permission.

(4) A party may not introduce expert evidence without the court’s permission if the expert has not complied with a direction under this rule.

The Practice Direction: DUTIES of EXPERT WITNESSES

The Criminal Procedure and Investigations Act (CPIA), 1996

In the course of any investigation, all the material gathered divides into two parts, used and unused.

Used material is the evidence in the case.

Unused material is all the information generated by the investigation that is not being used as evidence.

Used material = Must disclose;

Unused material = Disclosable!


Everything generated by the investigation in preparing the Crown’s case …


  • Investigator & medical experts’ records, notes, emails, photographs
  • Training and Competence records;
  • Validation records – eg; processes, software algorithms
  • Accreditation records – eg; people or processes
  • Certification records– eg; machinery, security
  • Compliance records – eg; SOPs, cleaning /anti-contamination systems
  • Continuity records….


Investigators and prosecutors are statutorily obliged to consider all such unused material and apply the Disclosure test as follows:

Is the unused material relevant to the case?

Prosecutors (not Investigators*) then consider:

If relevant, does the unused material either assist the defence case or undermine the prosecution case?

If the answer is ‘yes’, then the unused material must be disclosed to the defence. 

Fit for Purpose? Whose Purpose? Who is the End User?

“Fit for law enforcement purpose necessitates inclusion of CJS purpose from the commencement of investigations” (Parliamentary Science & Technology Select Committee Report, 2013’):

Investigation process must recognise that evidence (Prosecution) and intelligence (unused material) will pass through prosecution process (filter);

Enabling fitness for Prosecution processes requires;

  • Frontloading the criminal justice systems’ requirements – not just Courts!
  • Awareness of the impact of Code for Crown Prosecutors upon investigations;
  • Mandatory compliance with the Criminal Procedure Rules
  • Ensuring at point of investigative engagement that all expert witnesses comply with requirements set out in the Criminal Procedure Rules


In R v Reed, Reed [2009] the Court of Appeal dealt with the complex science of admissible DNA evidence, ordered that a "primer" or guide to the basic science applicable should be provided - no reason why such a document should not be agreed and provided to a jury in cases of NAHI (para 28)

The Court clearly set out and emphasised the importance of the use of and adherence to Rule 33 (now Rule 19) of the CrPRs (paras 128 – 131);

Parties must provide identification of agreement and disagreement within the experts' reports.

That notification of those areas of disagreement thereafter must be given to the court and the case then must be brought before the judge. This obligation falls to both the prosecution and the defence.

The judge should then order a meeting of experts to take place.

A statement under Rule 33.6 (now 19.6) should be then drafted setting out in clear terms the agreed science, for use at trial.

Any non-observance of an order for such a statement will be met in most cases by a refusal by the trial judge to admit the evidence of the expert not complying.

Finding Experts:

The CPS does not hold a register of experts - not in a position to quality assure individuals or organisations who provide expert witness services to the CJS, other than duty on a case by case basis.

The National Crime Agency (NCA) can provide information about experts in certain fields.

Forensic Science Regulator is now responsible for setting applicable validation (for scientific processes) and accreditation (for individuals) quality management standards.

Principal commercial organisations in England and Wales representing the interests and services of a variety of expert witnesses available via Internet.

Information on experts should be obtained from professional representative / regulatory body, eg; Medical professionals, Home Office FP Register etc

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