Forensic Voice Comparison Expert Reports

In a forensic voice comparison, an audio recording (recorded evidence) connected with a criminal act is compared with the recording of a suspect. The result of this comparison is a probabilistic statement relevant to the identity or non-identity of the speakers involved.

Forensic voice comparisons are carried out in the context of civil and criminal law cases. Auditory analysis and various kinds of acoustic analyses are applied, documented and presented according to international best practice. In most of voice-comparison's casework, recordings were obtained via long term interception and surveillance in organized and gang related crime.

Since 2013 uses the VOCALISE automatic speaker recognition software by Oxford Wave Research. VOCALISE is state-of-the-art speaker recognition technology, which integrates case-relevant system validation using the OWR-software Bio-Metrics.

VOCALISE: Acoustic distance of one voice to itself and other voices

Language analysis in forensic speaker comparison provides services both nationally and internationally, involving audio recordings in a variety of different languages. More than half of voice-comparison's cases are not about German or other Germanic languages, and are therefore carried out with the support of linguistic experts and professional court interpreters who are native speakers in their respective language. In order to provide in-depth analysis of variations within or between speakers, forensic expert witnesses working in court and doing case work have put forth this as a recommendation in their Code of Practice.

Forensic Speaker Profiles

In situations in which no suspect is in the frame yet, provides a speaker profile also known as forensic voice analysis. Speaker profiles constitute a scientifically based estimation of information on a speaker, including region, age, and first-language background.

Forensic Transcriptions is experienced in providing orthographic and/or phonetic transcripts of audio and video recordings with reduced intelligibility. Transcripts are provided both for investigative purposes as well as evidence in court. If the focus of interest is narrowed down to a short utterance with possible, alternative pronunciations, disputed utterance or questioned content analysis can provide a decision on the most likely alternative, using phonetic and linguistic methods.

Expert Witness Testimony

Dr Jessen has given expert witness testimony in cases over a period of nearly two decades. German law requires an expert witness to be present and available for questioning during the relevant time of a trial if that expert was individually appointed by a chamber as an independent specialist.

Additional services has provided numerous additional services for law enforcement and courts. Please request information if you would like to know more about this.

When a request falls partially or fully outside its competence spectrum, will make suggestions on possible procedures to guide you towards a viable solution, recommend professional experts and specialists, or it will propose an arrangement where some aspects of the case are addressed internally and others externally and where both parts can be integrated within one report.


Requests for expert work in forensic speaker identification and audio analysis come from the courts (criminal and civil law cases), prosecutors, defense attorneys, from police departments (usually crime divisions), or from customs. Dr Jessen also provides expert reports for government agencies whose jurisdiction might require forensic analyses, as well as for their contractors and affiliates. Dr Jessen provided expert witness testimony, often with several appointments, in more than 40 courts, mainly criminal law, within Germany alone: