> You would need to prove that they _could not have seen_ the testimony they provided.
A problem with this is that people giving false eyewitness testimony often believe they genuinely did see the thing they could not have seen and are telling the truth. So, a system like this would have the potential to punish as "liars" people who simply fell victim to what seem to be built-in foibles of the human memory system.
(Note I'm not doubting that some witnesses really are consciously lying. The problem would be the potential to sweep up the innocent with the guilty, if the standard used is "what they said they saw is impossible, therefore they are lying." Additional factors showing they were consciously lying would be needed.)
We already have sorted through this problem as a society.
The standard for perjury is not "their testimony was inaccurate, or was false". The standard for perjury is "they _knowingly_ made false testimony".
My complaint is not about changing the standard for perjury. My complaint is that prosecutors often avoid a perjury charge towards police, even when there is the evidence to support a perjury charge.
A problem with this is that people giving false eyewitness testimony often believe they genuinely did see the thing they could not have seen and are telling the truth. So, a system like this would have the potential to punish as "liars" people who simply fell victim to what seem to be built-in foibles of the human memory system.
https://www.scientificamerican.com/article/do-the-eyes-have-...
https://agora.stanford.edu/sjls/Issue%20One/fisher&tversky.h...
(Note I'm not doubting that some witnesses really are consciously lying. The problem would be the potential to sweep up the innocent with the guilty, if the standard used is "what they said they saw is impossible, therefore they are lying." Additional factors showing they were consciously lying would be needed.)