European guideline for evaluative reporting in forensic science

The European Network of Forensic Science Institutes (ENFSI) is working towards a full implementation of the logical principles of evidence interpretation and reporting in nearly sixty forensic laboratories in Europe. A project group has drafted a guideline for this purpose. The Netherlands Forensic Institute (NFI) was closely involved in this process.

The guideline suggests a standardized approach for interpretation and reporting based on hypotheses and so-called likelihood ratios, used by experts to express evidentiary value. The NFI has deployed this approach institute-wide since 2010.

Forensic examiners usually express the evidentiary value in verbal terms, such as ‘the findings of the analysis are much more probable when hypothesis 1 is true than when hypothesis 2 is true’. Since November of last year, the NFI uses a numerical definition to express just how much more probable ‘much more probable’ is. The laboratories that have joined ENFSI are now to follow this example.

Meeting the needs of the legal world

Another key part of the guideline states that laboratories should do their interpretations and reporting as much as possible at activity level. Experts are currently often reporting at source level.

“The ‘source level’ deals with the question of by whom, or by what, the trace was left. But lawyers are also particularly interested in knowing by which activity the trace was transferred. This may help to reconstruct what happened at the crime scene, and in the end it’s all about whether the accused carried out the alleged criminal activity. As a result of this improved manner of reporting, forensic science can better meet the needs of the legal world”, explains Charles Berger. He is one of the principal scientists of the NFI, and was a member of the ENFSI core group that drafted the guideline.

High requirements

The NFI has already implemented the approach that uses likelihood ratios and numerical definitions. As a part of the innovation programme ‘Beyond the Source’, the NFI is also working on methods that can be used by experts to interpret and report at activity level in various forensic disciplines.

In addition to the guideline, the project group also formulated a road map. “It states the steps a laboratory should take to comply with the guideline. The guideline sets high demands, to which we did not want to make any concessions. The road map will help laboratories implement the guideline.”

Leading group

“With this initiative, the NFI – together with the forensic laboratories in Sweden, Switzerland, and Ireland – forms the international leading group with regard to this issue”, says Berger. “We have been able to take great steps forward by involving the requesters and readers of our reports. Their say is important because in the end they are the ones who will have to work with our reports.”