I don't think either is a liar.

Memories are notoriously unreliable.  So are observations of the same events.  There are lots of scientific articles on memory distortion and event interpretation.

A famous experiment involved a law school class being interrupted by a scene where someone stabs someone else with a banana.  Then the professor asks the students for their eyewitness accounts.  The accounts differ dramatically.

The legal profession recognizes the limits of direct observation:

The legal system always has relied on the testimony of eyewitnesses,nowhere more than in criminal cases. Although the evidence eyewitnesses provide can be tremendously helpful in developing leads, identifying criminals, and exonerating the innocent, this evidence is not infallible.
Even honest and well-meaning witnesses can make errors, such as identifying the wrong person or failing to identify the perpetrator of a
crime.