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Voice recordings as evidence: proving they are authentic and who is speaking

Author: Mario Pareja Nieto, Computer and Telecommunications Engineer · Updated:

WhatsApp voice notes, recorded calls and audio messages are increasingly submitted in court. If the other side challenges them, two questions must be answered: have they been tampered with? And who is speaking?

Integrity: has the audio been altered?

  • The file's metadata is checked for consistency with the device and date.
  • Spectrogram analysis can reveal cuts, splices or abrupt background changes.
  • The continuity of ambient noise and recording characteristics is checked.

Identity: who is speaking?

  • A reference sample of known origin from the person is needed, such as an official recording or a statement.
  • Voice and speech features are compared between the reference sample and the disputed recordings.
  • Other data, such as phone bills or call logs, can support the conclusion.

How to keep recordings

  • Keep the original file on the device where it was received or recorded; do not forward or convert it.
  • Do not delete the conversation from the app.
  • Keep the device: the expert may need to extract the file directly.

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