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Forensic Voice Identification

Forensic Speaker Comparison, Speech Analysis, Voice Identification or Speaker recognition all refer to the process and science of giving an opinion as to whether an unidentified voice (e.g. a hoax caller) can be said to be consistent with a known voice sample obtained by recorded interview or other controlled means. Our speaker recognition expert uses linguistics & phonetics combined with computerised analysis and essential listening skills to determine the level of consistency between the known and the unknown voices.

Professional opinion is given as a level of consistency between the known and unknown speakers allied with any distinctive features that strengthen the opinion that the unknown and known speakers are the same. The members of the International Association of Forensic Phonetics and Acoustics [IAFPA] have an agreed scale of consistency outcomes linked with levels of distinctiveness that they use to describe their results and opinions within the body of their reports.

  • Consistency Outcomes - Consistent, Not consistent, No decision
  • Consistent Outcome - Distinctiveness

The decision that two samples are consistent with having been spoken by the same person does not necessarily entail that they were. Unless the cluster of features leading to the consistency decision is distinctive or unusual, they will be shared by a substantial number of other people in the population. Therefore it is necessary to proceed to evaluate the distinctiveness of the features common to both sets of samples. A convenient way of assigning an overall rating to the distinctiveness of the common features is to locate them on a five-point scale, as follows:

5. Exceptionally distinctive - the possibility of this combination of features
being shared by other speakers is considered to be remote
4. Highly distinctive
3. Distinctive
2. Moderately distinctive
1. Not distinctive

Infra Tech Forensics will review and give expert advice on the viability of a speaker identification case before any charges are incurred.


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