My vague understanding is that you are allowed to enter evidence to impeach someone (show that they are lying) at any time, most notably right after they lied.

I cound be wrong, but this trial has not inspired confidence in the judge actually following the law so I'm not taking the court ruling otherwise as the strong evidence that I normally would.

> My vague understanding is that you are allowed to enter evidence to impeach someone (show that they are lying) at any time, most notably right after they lied.

In England and Wales, yeah, as long as the other rules are met (it's of value, relevant, not extremely prejudicial to the defendant, not hearsay, etc.)

You wouldn't impeach them though. It could be perjury if they lied under oath, but otherwise it would just be standard discrediting of a given person.

For some reason calling into question the credibility of a witness is generally called impeaching them in common law... never figured out why. Why isn't that the right term here?

I have no clue about the UK, but are their laws such that state attorney are allowed to actively lie to a judge and make false statements?

In the UK, all lawyers have an overriding duty to the court. This means they must not mislead the court. Doing so can lead to losing the ability to practice law.