Recordings as Evidence - Technology Behind Tamper Detection

Audio recordings are more than just meeting notes. They’re increasingly used as legal evidence—proof of harassment, records of contract negotiations, medical consultations. But if you can’t verify “when was this actually recorded?”, the evidentiary value plummets.

File Timestamps Are Easy to Tamper With

Audio files on your computer or smartphone have a “modified date” recorded by the filesystem. But this information is surprisingly easy to change. On Mac, a single command like “touch -t 202301011200 file.m4a” changes the timestamp to any date you want. On Windows, free tools like BulkFileChanger, Attribute Changer, or PowerShell’s Set-ItemProperty can do it in seconds.

This means if you submit a file’s “modified date” as evidence, the opposing party can simply argue “it could have been tampered with”—and you’d have no good rebuttal. Courts and arbitration require more trustworthy timestamp information.

Recording Time Embedded in Containers

MP4 and M4A audio files have an internal structure called a “container” separate from the filesystem. The MOOV atom within contains a creation_time written by the recording device. iPhone Voice Memos, Android recording apps, IC recorders—most devices automatically record this information.

Nikke analyzes this container information to display the most accurate recording date possible. By prioritizing the timestamp recorded by the device over the file’s modified date, we provide more trustworthy time information.

Why Container Tampering Is Difficult

To tamper with the timestamp inside a container, you need to either edit the file directly with a binary editor or re-encode it with specialized tools like FFmpeg. But re-encoding changes the audio quality, detectable through waveform analysis. Binary editing also requires maintaining consistency with other metadata (duration, sample rate, etc.), making it difficult without expert knowledge.

In contrast, changing a file’s modified date takes one touch command or a few mouse clicks. This difference in difficulty translates directly to difference in evidentiary reliability.

Nikke’s 3-Tier Timestamp System

Nikke uses a 3-tier display system to visualize timestamp reliability. A ✓ mark indicates the timestamp was extracted from the container, while a ⚠ mark shows it’s estimated from the file’s modified date or upload time. This lets you judge at a glance how trustworthy the recording date is.

Nikke aims for transcription that can withstand evidence review in court. Beyond accurate transcription, the reliability of “when was it recorded?” is a crucial factor that determines evidentiary value.