DNA sampling in criminal investigations: order, cooperation and use

Section 123 StPO governs physical examinations. They are permitted, among other situations, where specific facts indicate that a person has left traces whose recovery and examination are essential for investigating an offence. In certain constellations, other bodily findings may also be relevant.

The prosecution generally orders the examination on the basis of judicial authorisation. In an emergency, the prosecution may order it provisionally but must obtain judicial authorisation without delay. Section 123(3) contains a specific rule allowing the criminal police to take a mouth swab themselves.

Section 124 StPO governs molecular genetic examination. It permits the examination of biological traces and material belonging, or likely belonging, to a particular person in order to attribute a trace or establish identity or parentage. The criminal police may arrange examination of a mere biological scene trace themselves. For other material, the provision generally requires an order by the prosecution based on judicial authorisation.

A mouth swab initially produces only examination material. The molecular genetic analysis creates the result that can be compared with a trace or a lawfully obtained comparison profile. A request for a sample therefore does not answer every question about later processing.

The relevant facts are the trigger, objective and scope. The file should show which allegation is being investigated, which trace or comparison question exists and why the measure matters for the investigation. A general DNA search without a defined purpose does not reflect the statutory structure.

The form of the intervention also matters. Section 123(4) StPO excludes operative interventions and interventions that could cause health impairment lasting more than three days. A mouth swab may be taken by a specially trained person. The record should make the measure and information provided understandable.

Section 124(1) StPO permits comparison with results of molecular genetic examinations lawfully obtained under the StPO or the Security Police Act. It therefore matters where comparison data came from and whether they may be used for the concrete investigative purpose.

Attribution is not a statement about the entire course of events. It may show that material can be attributed to a person. That alone does not establish when the material reached the location or who performed an act. Those questions belong to the overall assessment with the other evidence.

The defence should therefore read the trace record, chain of custody, comparison sample and expert instruction together. Inconsistencies in collection, labelling or storage can affect evidential weight and need to be identified precisely.

Under section 124(3) StPO, the molecular genetic examination must be assigned to an expert in forensic medicine or forensic molecular biology. The material must be supplied in anonymised form. Attribution to a person should be possible only to the extent required by the purpose of the examination.

The technical analysis has to be distinguished from the legal instruction. A report may explain a genetic match or exclude attribution. Its legal significance also depends on how the sample was obtained, how the trace was documented and what the other evidence shows.

Section 123(6) StPO sets specific conditions for using physical-examination results as evidence. The conditions for the examination must have existed, the examination must have been lawfully ordered and the use must serve the statutory proof purpose. Whether those conditions are met must be assessed from the file.

Section 124(4) StPO limits the use and processing of personal examination material and results. Once attribution to the trace or establishment of identity or parentage has been ruled out, the material and results must be destroyed.

Section 124(5) StPO also permits transmission to security authorities only where collection and processing would be lawful under the relevant security-police provisions. Further transfer is therefore tied to its own statutory conditions.

An application after the proceedings should identify the sample, profile or report concerned. It should also state the outcome of the proceedings, where the data are stored and which purpose is said to justify continued retention.