It would prove that there was insufficient cause to find the other party guilty. Proof that the party had lied could include. The officer admitting including to others in public or private that he had lied or that the facts were different in a substantive way from what he had previously testified.

Video that contradicts officers testimony.

Physical evidence that proves the testimony was a lie.

All of the above would have to be sufficiently different from reality that would suggest that its impossible to consider the possibility that the officer misremembered.

Example fake scenario:

I heard violent screaming coming from inside the home so I had to break down the door and search for the person in need of help and I just happened to find drugs.

Contradicted by video from the ring door bell which recorded the officer just walking up and kicking the door down so he could conduct an illegal search.

For real examples see the article. None of the listed scenarios suggest any reasonable party could think that the police officer misremembered.

I get your point, but that video as described would not contradict anything of the testimony.

> Well, if the accused is considered non guilty of what they said they saw them do, then doesn't that "prove" that they lied?

No. It absolutely doesn't prove that they lied. That's simply not what "not guilty" means in the criminal justice system.