Legal Question in Criminal Law in Washington

The standard is the same in a murder case as in any criminal case. The prosecution has the burden to prove the case beyond a reasonable doubt. Technically, the defense has no burden to demonstrate anything. But practically, especially in serious cases, the jury expects the defense to show how they did not commit the crime.

A very common defense is just to argue that the government failed to meet it's burden of proof, and that even if the jurors suspect the defendant's guilt, the law requires that they acquit.