In a criminal trial, if the parties exchange the witness' lists during discovery, isn't there a risk the witnesses are coerced, murdered, etc?

Sure. The Mafia in the US was known for witness intimidation. My guess is that gangs do the same thing.

But the law is that witnesses are to be announced and shared by the parties, and (usually) deposed, so that their testimony can be properly questioned and verified.

What could happen to the jurors is the premise of the novel Th1rt3en (“Thirteen: The Serial Killer Isn’t on Trial. He’s on the Jury.”), by Steve Cavanagh. A very creepy story, and just plausible enough to chill you.

@Jeruba: I admit not having read it (though I have it), but can’t they at least declare the juror “tainted” and dismiss the trial?

I’m no expert on jury process, and I’m not trained in the law. I just thought you might be interested in a popular and enthusiastically reviewed treatment of a theme closely related to your question.

It’s true and possible. And there is nothing that can be done about it until it happens. You can’t assume someone is guilty of a crime they haven’t committed.

See witness protection programs .

@Zaku: The program refuses to relocate most witnesses who have a criminal record or a drug problem, or are unemployed, saying that to do so might send criminals into unsuspecting cities and neighborhoods. It doesn’t help against street gangs (check Howard Roberts, who saw the murder of a witness, Carmen Estronza, November 2004, because of his record).

They also have short-term protection up till the testimony is complete, where they stick the witness in a hotel somewhere under guard, etc.

I think it’s common procedure for the prosecution to request the judge protect the witness by not informing the defense of the witness’ exact identity before the trial.

The risk tends to depend on the accused. If they’re not part of a dangerous group, the accused being in prison until the trial may tend to prevent their interference. Also for most people, the potential legal consequences of messing with jurors would tend to be a deterrent. Against organized crime or the super-rich, there are multiple possible agents who might try something, but testimony is deposed before the trial, and if it changes materially for the trial, or something happens to a witness, that can backfire for the accused, and expose them and/or others to new charges.

These and other points are covered in such places as:

https://www.cps.gov.uk/legal-guidance/witness-protection-and-anonymity

https://www.unodc.org/documents/middleeastandnorthafrica/organised-crime/Good_Practices_for_the_Protection_of_Witnesses_in_Criminal_Proceedings_Involving_Organized_Crime.pdf

https://pceinc.org/wp-content/uploads/2016/07/20160610-Witness-Intimidation-What-You-Can-Do-To-Protect-Your-Witnesses-PCE.pdf

@Zaku: Thank you! I understand more now.