Based on my 28+ years working with the human voice for identification purposes, I have been asked on several occasions to determine a person’s identity based on a voice sample when an exact exemplar was not available. I call this nontraditional voice identification. I do not make this type of voice identification a day to day practice and I always let our clients know that my findings are preliminary based on experience rather than exact science.
One example is the Elvis Presley voice identification I did. Since Elvis is dead, I could not record an exact exemplar.
Because the family who produced the song was convinced it was Elvis and needed my opinion, I compared the unknown song to known Elvis Presley songs from the same timeframe. My opinion was that the new song is the voice of Elvis. Not everybody agreed with my opinion, however. Since science was not involved, these people had reason to base their opinion on their personal knowledge of Elvis Presley’s style.
The above Elvis story is a good example of nontraditional voice identification. An emergency situation is another example, such as when a threatening call was made with intent to do bodily harm to a person or persons. Emergency voice identification becomes necessary to provide the authorities with evidence so they can order the accused to cooperate and provide the voice identification expert an exact exemplar.
One scenario is when a bomb threat call is made to a place of business. Voice identification becomes necessary to determine if the threat was made by a previous employee. I have worked on cases like these many times. Management often has an idea of who made the threat. Their opinion is based on more information than a voice identification expert would use such as discharge date, personality characteristics and work history. I would conduct an emergency voice identification using known samples of the accused person’s speech, like voice mail recordings when the suspect employee called in sick.
Here are the steps I take for emergency voice identification:
1. Locate a known sample of the accused voice
2. Locate the threatening voice recording
3. Make a list of all speaking characteristics of the known voice. These include stutters, vowel pronunciation, any other speech observations and consistent speaking styles that can be observed.
4. Make a list of all speaking characteristics of the unknown voice. Are there any similarities or differences that can be assessed?
5. Use a spectrum analyzer to note voice spectrum of both samples. Are the samples close enough in spectrum to be a match or different enough to help arrive at a conclusion?
The voice identification expert’s task is to take all information from critical listening, spectrum analysis or electronic measurement, and visual inspection of the wav formation and decide if the voice in question is the same voice or not. The next step is to have the law enforcement officials use the voice identification expert’s report to encourage the suspect to cooperate and record an exact exemplar.