Practical cases in forensic image comparison

Typical cases

The scope of the finding depends on image quality, comparability, the comparison basis, and the evidential question.

Typical cases differ according to the type of proceedings, the state of the material, and the evidential question. Image material, comparison basis and instruction determine the working route.

Early clarification separates preliminary review, technical preparation and written expert reporting.

Typical casesDriver identification · Criminal matters · Preliminary review of image suitability · Comparison findings
What it is aboutClarify the evidential question · Review the state of the material · Make limits visible early
Practical benefitRapid orientation before the actual instruction

Typical cases · Regulatory contexts

Driver identification

In the administrative fine context, driver identification is the most frequent case group. The typical case is often not clear-cut. It is the case in which a measurement image does not simply speak for itself. The question then arises whether facial regions, the ear region, the hairline, chin contour, or other visible structures are available in sufficient quality and whether suitable comparison images exist.

In practice, even before the actual expert report, the question is often whether a full instruction is worthwhile at all. Especially where the angle of view is very unfavourable or there is substantial occlusion, it may initially be possible only to review image suitability.

These are case-related questions with a clear evidential question and direct relevance to the proceedings. Driver identification shows in particular that expert examination is often needed in borderline cases, not only in clear-cut cases. Typical questions are: Is the depicted person identical with the named comparison person? Which features speak for or against identity? Is the image quality sufficient for a full assessment? Are additional comparison images required, or is only a preliminary review possible at first?

Typical cases · Further proceedings

Criminal matters and other image sources

In criminal matters, the initial situation is often more heterogeneous. Image material may derive from video surveillance, the vicinity of the crime scene, cash machines, public recordings, or private security systems. Sequences, partial occlusions, differing recording situations, and investigations already under way are often added. Comparable questions may also arise in document and passport cases or with historical image sources where an anthropological comparison report is required for clarification or attribution.

The emphasis then shifts more strongly to comparability, documentation, and the evaluation of investigative measures already taken. The more preselection, witness nomination, or wanted-person circulation is involved, the more important the transparent presentation of the path by which the named person came into focus becomes.

Typical cases · Assignment framework

Preliminary review instead of full expert report

Not every enquiry has to lead immediately to a full expert report. In many cases, a short professional preliminary review is more sensible. It clarifies whether the available questioned image is suitable for assessment, whether additional comparison material is required, or whether technical preparation or conversion should come first.

This preliminary stage limits effort and avoids instructions whose result would already be very limited for methodological reasons.

Typical cases · Bias and evaluation

Preselection as a particular risk situation

If a person has already come into focus because of external similarity, a witness nomination, a wanted-person measure, or a technical hit list, a preselection situation is likely to exist. In that case, later similarity can no longer be read as neutral. Precisely for that reason, this prior history must be disclosed in the report and taken into account in the evaluation.

For courts and authorities, this is important in practice: information on whether and how a named person came into focus changes the later expert assessment.

Helpful are details about the questioned image and about the case background, investigative measures already taken, photo line-ups, witness nominations, or other prior identifications. With poorly framed instructions or unsuitable source material, unnecessary follow-up questions can arise. Early clarification of the case, the evidential question, and the material basis usually reduces this risk.

Typical cases · Material and enquiry

Practical enquiry

A brief description of the case background, the exact evidential question, information on the available questioned image, and any investigative or nomination steps already taken are helpful. This helps clarify the case type, the material problem, and the instruction needed for an expert examination at an early stage.