Forensics
If the science says it is a match, is the case not over?
No, and the reason is structural rather than a matter of caution. Examiners answer questions about material; courts answer questions about people. Two legal systems make the boundary visible in their own texts — one by bounding what an examination may determine, the other by bounding what an expert may say.
In short
A forensic examination produces a statement about material: what a substance is, whether two samples share characteristics, what a record contains. A criminal case asks something else: whether a particular person did a particular thing, with a particular state of mind, in circumstances the law defines. The gap between those two questions is not a gap in the science. It is the difference between a measurement and a verdict.
Why it exists
AnalysisThe confusion is not the public’s fault. A forensic result arrives with the authority of a laboratory and the vocabulary of certainty, and it is usually reported as though it answered the question everyone is actually asking. It rarely does. A finding that two samples share characteristics leaves open how the material got there, when, and whether its presence means anything at all.
How it works
German law draws one half of the boundary at the earliest possible point: it bounds what the examination may even ask. Section 81e of the Code of Criminal Procedure permits a molecular-genetic examination to establish the DNA identification pattern, parentage and the sex of the person, and to compare those with reference material, so far as necessary to investigate the facts. It then adds: Andere Feststellungen dürfen nicht erfolgen; hierauf gerichtete Untersuchungen sind unzulässig — other findings may not be made, and examinations directed at them are inadmissible.
The narrow exception proves the rule. Section 81e(2) permits examination of found, secured or seized material, and where it is unknown which person trace material came from, findings about eye, hair and skin colour and about age may additionally be made. The extra findings are permitted precisely where there is no person to compare against — and they stop at externally visible characteristics.
England and Wales draws the other half at the point of testimony. Under the Criminal Procedure Rules an expert must give opinion that is objective and unbiased and within the expert’s area or areas of expertise, must define that area both in the report and when giving evidence, and — when giving evidence in person — must draw the court’s attention to any question to which the answer would be outside it.
AnalysisThe two provisions approach the same boundary from opposite ends — one limits the examination, the other limits the testimony — and neither leaves the decision to the examiner’s modesty. That is the point: a boundary that depended on individual restraint would fail in exactly the cases where the pressure to cross it is greatest.
It is worth stating what forensic science does do, because the boundary is not a criticism. In its own account of why it reviews forensic methods, the United States National Institute of Standards and Technology observes that forensic science can help investigators solve crimes, and that it can help exclude innocent people from an investigation or exonerate them in cases of wrongful conviction.
Common misconceptions
Widely held beliefs that do not match how the system actually operates.
Common belief: A forensic match proves the person did it.
In practice: A match is a statement that two samples share characteristics. How the material came to be where it was found, when, and whether that matters are questions the examination does not address and the court must.
Common belief: The expert decides the case when the evidence is scientific.
In practice: The Criminal Procedure Rules require an expert to keep opinion within their area of expertise and to tell the court when a question falls outside it. Deciding the case is outside every expert’s area of expertise.
Common belief: A sample can be tested for whatever the investigation wants to know.
In practice: Not in German law. Section 81e permits a defined list of findings and provides that other findings may not be made and that examinations directed at them are inadmissible.
Common belief: Saying forensic science cannot decide guilt is a criticism of forensic science.
In practice: It is a description of what the discipline is for. NIST notes that forensic science can exclude innocent people from an investigation and exonerate them in cases of wrongful conviction — which is the boundary working, not failing.
How this varies between jurisdictions
A required section on every guide. Arrangements differ between countries, and we say how.
Two systems, two ends of the same boundary.
- Bound what the examination may determine, by statute — Germany, StPO § 81e.
- Bound what the expert may say, by procedural rule, and require them to flag questions outside their expertise — England and Wales, Criminal Procedure Rules 2025 Part 19.
- A narrow exception where there is no person to compare against, limited to externally visible characteristics and age — Germany, StPO § 81e(2).
Rights and accountability
AnalysisThe boundary is what makes forensic evidence contestable. A conclusion stated within a defined scope can be tested against that scope; a conclusion about guilt cannot be tested at all, because no method supports it.
It also determines what a defence can ask for. Where the expert must define their area of expertise in the report, the definition itself becomes something to examine — and a question that falls outside it is one the expert is obliged to identify rather than answer.
What we could not establish
- Two legal systems are described from primary text. How courts in either weigh forensic evidence in practice is case law this platform has not researched.
- This page describes the boundary between examination and adjudication. It does not describe admissibility rules, which differ in every jurisdiction and are not set out here.
Where to go next
Related: expert evidence in court, the limits of forensic evidence, and what forensic science is.
Related topics
- Whose expert is the expert?
Two systems answer that differently and both are answering the same worry — that an expert paid by one side will start arguing for it. Germany removes the party from the choice: the judge selects the expert. England and Wales keeps the party and subordinates the loyalty.
- How reliable is forensic evidence?
That question has no single answer, and the reason is the finding. Published scientific-foundation work shows the same technique can be highly reproducible on one kind of sample and produce a wide range of results between laboratories on another.
- What is forensic science?
Forensic science is the application of scientific methods to questions arising in legal proceedings. This guide explains what it can establish, where its limits lie, and how its reliability is assessed.
Sources
Strafprozessordnung (StPO) § 81e — Molekulargenetische Untersuchung (German original text)
Bundesministerium der Justiz / Bundesamt für Justiz (Gesetze im Internet) · Legislation · link verified 2026-08-26
The authoritative German text, read directly. Supports § 81e(1): on material obtained under § 81a(1) or § 81c, molecular-genetic examination may establish the DNA identification pattern, parentage and the sex of the person, and compare those findings with reference material, so far as this is necessary to investigate the facts — followed by "Andere Feststellungen dürfen nicht erfolgen; hierauf gerichtete Untersuchungen sind unzulässig": other findings may NOT be made, and examinations directed at them are inadmissible. Supports § 81e(2): examinations permissible under subsection (1) may also be carried out on found, secured or seized material; where it is unknown which person trace material came from, findings about eye, hair and skin colour and about the age of the person may additionally be made; and where the person is known, § 81f(1) applies correspondingly. Cited for the fact that a legal system can bound by statute what a forensic technique is permitted to determine. It supports no claim about the reliability of DNA analysis, no claim about databases or retention, and nothing about any other country.
The National Archives (legislation.gov.uk) · Legislation · 2025 · link verified 2026-08-26
The official text of the current Rules, read directly. NOTE ON CURRENCY: the Criminal Procedure Rules 2020 (S.I. 2020/759) were REVOKED with effect from 6 October 2025 by these Rules; the 2020 text was fetched first and legislation.gov.uk records it as revoked, so the 2025 Rules are cited instead. Supports r. 19.1: the Part applies where a party wants to introduce expert opinion evidence, and an "expert" means a person required to give or prepare expert evidence for the purpose of criminal proceedings, including evidence required to determine fitness to plead or for the purpose of sentencing. Supports r. 19.2: "An expert must help the court to achieve the overriding objective" by giving opinion which is "objective and unbiased" and "within the expert's area or areas of expertise", and by actively assisting the court in its case-management duty; r. 19.2(2): "This duty overrides any obligation to the person from whom the expert receives instructions or by whom the expert is paid"; r. 19.2(3): obligations to define the expert's area of expertise in the report and when giving evidence, to draw the court's attention to any question whose answer would be outside that area, and to inform all parties and the court if the expert's opinion changes. Supports r. 19.4, the required content of an expert's report, including: qualifications, relevant experience and accreditation (a); the literature or other information relied on (b); the substance of all material facts given to the expert (c); where there is a range of opinion, a summary of that range and reasons for the expert's own opinion (f); any qualification the expert must attach to an opinion (g); "such information as the court may need to decide whether the expert's opinion is sufficiently reliable to be admissible as evidence" (h); a summary of conclusions (i); a statement that the expert understands and has complied with the duty to the court (j); and the same declaration of truth as a witness statement (k). Rules in force 6 October 2025. ENGLAND AND WALES only, extent-marked "E+W". It supports nothing about Scotland or Northern Ireland, nothing about civil proceedings, and no claim about how any court weighs expert evidence in practice.
Scientific Foundation Reviews — Forensic Science Program
National Institute of Standards and Technology (United States) · Government publication · link verified 2026-08-26
NIST's own account of the programme, read directly. Supports: that the reviews identify the scientific foundations underpinning forensic methods, document and evaluate the empirical evidence for their reliability, explore their capabilities and limitations, and identify knowledge gaps; that the method is set out in NISTIR 8225 and proceeds by selecting a discipline, gathering scientific literature and publicly available information, convening NIST scientists and outside experts, publishing a draft for public comment, and finalising after considering comments; that the programme fulfils a need identified by the 2009 National Academy of Sciences report, which called for "studies establishing the scientific bases demonstrating the validity of forensic methods"; that in 2016 the National Commission on Forensic Science recommended NIST conduct independent scientific evaluations of technical merit; and that Congress appropriated funds for the reviews from 2018. Supports NIST's own statement that forensic science "can help exclude innocent people from an investigation or exonerate them in cases of wrongful conviction". Supports the STATUS of individual reviews as listed on that page: DNA Mixture Interpretation is a final report; the Bitemark Analysis review is NISTIR 8352-DRAFT with the public comment period closed. Nothing is quoted from that draft anywhere on this platform.