[mike_hearn]

Expert witnesses are already required to be impartial. There's currently an inquiry in the UK over a massive miscarriage of justice caused by an expert witness going rogue and letting prosecutors put words in his mouth, etc. A big part of the scandal is that prosecutors were meant to inform him of his legal duty to be neutral and share all the facts, but they didn't, so now he's claiming he didn't realize he was required to share all relevant facts including those negative for the prosecution.

[TimTheTinker]

There's a difference between a requirement and its enforcement.

I'm arguing for better enforcement via law, to ensure witnesses are either impartial or prosecuted for impartiality.

If partial witnesses aren't being prosecuted, then launch an inquiry and do a causal chain analysis. It's bound to turn up a root problem that is solvable.

[mike_hearn]

This is a common philosophical/ideological difference.

The left tend to argue that impartial people exist, and that they are numerous/easy to find.

The right tend to argue that there's no such thing as an impartial person, that you can get people who start out partial and do their best to be fair (e.g. judges) but it takes constantly training, reinforcements and incentives to do that and there's always the danger of slipping back. You definitely can't assume it.

The adversarial court system is based on the right-leaning belief: although expert witnesses are told to be impartial, the system doesn't assume this is enough and so witnesses are called by one side and cross-examined by the other. The lawyer's job is to sniff out any signs of bias or incompetence.