Codes of Conduct for Forensic Experts

Every major code of conduct for forensic experts rests on three duties that define the expert's role as a servant of the court rather than an advocate for a party. These duties appear under different names in different systems but describe the same obligations.

The duty of independence requires the expert to form and express opinions based solely on the evidence and professional judgment. It prohibits the expert from adjusting conclusions under pressure from lawyers or clients, advocating for one side's version of events, or suppressing findings that contradict the case being advanced. In England and Wales, Criminal Procedure Rules Part 19.2 states explicitly that an expert's duty to the court overrides any duty to the party from whom the expert has received instructions or by whom the expert is paid. The American Academy of Forensic Sciences Code of Ethics uses similar language, prohibiting misrepresentation and requiring members to avoid conflicts of interest. India's Bharatiya Sakshya Adhiniyam 2023 does not codify a duty of independence in the same procedural form, but courts have consistently applied the principle in assessing expert credibility.

The duty of competence limits the scope of permissible opinions to areas where the expert has genuine expertise and applies methods that are scientifically validated. An expert who opines outside their validated domain, uses a method that lacks scientific support, or fails to stay current with developments in the field breaches this duty. In the US, Federal Rule of Evidence 702 requires the expert's opinion to be based on sufficient facts or data, rest on reliable principles and methods, and reflect a reliable application of those principles to the facts. The UK Forensic Science Regulator's Codes of Practice and Conduct require practitioners to use only methods that have been validated and are fit for purpose.

The duty of disclosure requires the expert to place all material findings before the court, whether favourable or unfavourable to the instructing party. This includes negative results, the limitations of the analytical method, the range of the method's error rate, and any known expert disagreement about the interpretation of the type of evidence involved. In England and Wales, Practice Direction 19B requires the expert to state the substance of all instructions, even those not relied upon. The US Federal Rule of Civil Procedure 26(a)(2)(B) requires a written report disclosing the basis and reasons for all opinions. Selective disclosure, presenting only the findings that support the instructing party, has been treated by courts as a deliberate distortion of the evidence.

No single binding global code governs forensic experts. Each jurisdiction maintains its own framework, but the underlying duties converge. The table below summarises the main sources in three jurisdictions.

In England and Wales, the Forensic Science Regulator (a statutory role created by the Forensic Science Regulator Act 2021) has powers to require forensic providers to comply with a Code of Practice, and can intervene when a provider's conduct falls below the required standard. This represents a formal regulatory layer that sits above professional body membership and court rules. Most other jurisdictions have not yet created an equivalent statutory regulator specifically for forensic science.

In India, Section 39 of the Bharatiya Sakshya Adhiniyam 2023 provides the statutory basis for admitting expert opinion on matters requiring special knowledge. The section does not enumerate conduct duties directly, but Indian courts have, through case law, required experts to be impartial and to disclose the basis of their conclusions. The Central Forensic Science Laboratory (CFSL) operates under the Ministry of Home Affairs and is subject to internal quality standards, but there is no national statutory code of conduct equivalent to England's Regulator framework. The Digital Personal Data Protection Act 2023 adds a further dimension for digital forensic experts handling personal data.

Courts respond to breaches of conduct duties along a spectrum from adverse comment to full exclusion of evidence. The severity of the response depends on whether the breach was inadvertent or deliberate, whether it affected the reliability of the opinion, and whether it caused injustice.

Exclusion is the most immediate courtroom consequence. In the UK, if an expert has failed to comply with Practice Direction 19B, the court may refuse permission to call the expert or may direct the expert to provide a further report. In the US, the trial judge acting as gatekeeper under Daubert may exclude the testimony before trial if the methodological requirements of Rule 702 are not met. A motion in limine challenging expert evidence on conduct grounds is a routine feature of complex US litigation.

Beyond the courtroom, professional bodies can impose their own sanctions. Membership can be suspended or revoked, and a practitioner whose name is removed from an expert register loses the ability to give court evidence in cases requiring registered experts. In jurisdictions with statutory regulation, such as England and Wales under the Forensic Science Regulator Act 2021, a provider that loses compliance status loses the ability to supply forensic services to the criminal justice system. Disciplinary outcomes are increasingly published, which creates a reputational consequence that extends beyond any single case.

Civil liability is a further exposure. An expert who provides a report knowing it is false, or who is grossly negligent in its preparation, may be sued for damages. Most jurisdictions provide some immunity to expert witnesses for evidence given in court, but the scope of that immunity varies. In England and Wales, the Supreme Court in Jones v Kaney (2011) removed witness immunity from expert witnesses in civil proceedings, meaning a negligent expert can now face a negligence claim from the party that retained them.

The structural tension in forensic expert work is that the expert is retained and paid by one party but owes primary duties to the court. This is not a minor administrative inconvenience; it defines the expert's role and distinguishes the expert from an advocate.

The expert owes the client duties of reasonable care and skill in preparing the analysis, confidentiality over privileged instructions, and timely delivery. These duties are real and enforceable. But they are subordinate to the duty to the court. When a client instructs an expert to exclude unfavourable findings from a report, or to frame a conclusion more strongly than the evidence supports, the expert must refuse. When the expert discovers a finding that damages the client's case, the expert must include it in the report regardless of the client's wishes.

In practice the conflict often arises at the margins: a lawyer asks the expert whether a finding can be described differently; a client asks whether a conclusion can be expressed as a certainty rather than a probability; a retaining solicitor sends back a draft report with suggested edits that soften caveats. The expert's obligation in each case is the same: the report must reflect the expert's genuine opinion, stated with appropriate precision, regardless of how the retaining party would prefer it to read.

Competence is the most contested of the three duties in practice, because the boundary of a legitimate expert opinion is not always sharp. The duty requires the expert to opine only within their area of validated expertise, but defining that area requires judgment.

Accreditation provides one mechanism for assessing and signalling competence. ISO/IEC 17025 is the international standard for the competence of testing and calibration laboratories; a laboratory accredited to this standard by a national accreditation body (UKAS in the UK, A2LA in the US, NABL in India) has been independently audited against defined criteria for method validation, quality control, personnel competence, and documentation. Courts in multiple jurisdictions have begun to treat accreditation as a floor for forensic laboratory evidence, and the UK Forensic Science Regulator's Codes make accreditation mandatory for a growing list of forensic disciplines.

Professional bodies add a second layer. The Chartered Society of Forensic Sciences (CSFS) in the UK, the American Academy of Forensic Sciences (AAFS) in the US, the Australian and New Zealand Forensic Science Society (ANZFSS), and the Indian Association of Forensic Scientists (IAFS) each maintain codes of ethics that members must follow as a condition of membership. Membership of a recognised body is not a legal prerequisite for giving expert evidence in most jurisdictions, but it signals professional standing and provides a route for complaints against members whose conduct falls below the code.

Continuing professional development (CPD) obligations, which are a standard feature of most professional body codes, operationalise the competence duty over time. An expert who qualified ten years ago but has not kept pace with developments in the field, including changes in the scientific understanding of the method they use and its known error rates, is arguably not meeting the competence duty even if they were fully competent at the time of qualification. This matters particularly in fields where the science has moved quickly, such as probabilistic genotyping in DNA analysis and comparative bullet lead analysis, which was formally abandoned by the FBI in 2005 after the National Research Council found the underlying science unsound.

The relationship between a conduct code and admissibility is indirect but consequential. Courts do not enforce professional codes directly; they assess the reliability and credibility of expert evidence. But compliance with a recognised code is evidence of reliability, and breach is evidence against it.

In the US, the Daubert standard requires the trial judge to consider, among other things, whether the technique has been tested, whether it has been subjected to peer review and publication, whether a known error rate exists, and whether it is generally accepted in the relevant scientific community. These criteria map closely onto the competence and disclosure duties: an expert who has used a method without knowing its error rate, or who has not disclosed that the method lacks peer-reviewed support, has breached both duties and provided grounds for exclusion under Rule 702. The Supreme Court's decisions in Daubert v. Merrell Dow Pharmaceuticals (1993), General Electric Co. v. Joiner (1997), and Kumho Tire Co. v. Carmichael (1999) together established that this gatekeeping function applies to all expert testimony, not only scientific evidence in the narrow sense.

In England and Wales, the admissibility framework is less prescriptive about methodology than the US Daubert test, but the courts have developed similar principles through case law. The Court of Appeal in R v Dlugosz (2013) held that expert evidence must cross a threshold of reliability before it is admitted, and practice under the Criminal Procedure Rules increasingly requires experts to address in their reports the limitations of the method and the range of reasonable opinion in the field. An expert who overstates certainty, fails to disclose contrary opinion, or uses a non-validated method is vulnerable to both exclusion and cross-examination on the breach.

Under the Bharatiya Sakshya Adhiniyam 2023, Indian courts retain discretion to assess the credibility of expert evidence. Section 39 admits expert opinion on science, art, foreign law, or trade, and Section 40 allows the court to request a written report. Courts apply a practical admissibility screen based on the expert's qualifications and the apparent reliability of the method, though there is no Daubert-equivalent pre-trial gatekeeping procedure. The absence of a formal pre-trial gatekeeping mechanism means that conduct issues are more likely to arise during cross-examination than as a formal admissibility ruling before testimony begins.