California · Penal Code

PEN §1127b: When, in any criminal trial or proceeding, the opinion of any expert witness is received in evidence, the court shall instruct the jury substantially as follows: Duly qualified experts may give their

Civil

What this law says, in plain English

This statute requires courts to instruct juries on how to evaluate expert witness opinions in criminal trials, including that experts may testify, juries need not accept expert opinions as conclusive, and juries may disregard unreasonable opinions.

Read the full statutory text

When, in any criminal trial or proceeding, the opinion of any expert witness is received in evidence, the court shall instruct the jury substantially as follows: Duly qualified experts may give their opinions on questions in controversy at a trial. To assist the jury in deciding such questions, the jury may consider the opinion with the reasons stated therefor, if any, by the expert who gives the opinion. The jury is not bound to accept the opinion of any expert as conclusive, but should give to it the weight to which they shall find it to be entitled. The jury may, however, disregard any such opinion, if it shall be found by them to be unreasonable. No further instruction on the subject of opinion evidence need be given.

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This page is legal information, not legal advice. Code text is sourced from official publications and may lag amendments — always confirm at the official source linked above. Plain-English summaries and relationship data are AI-derived and reviewed on an ongoing basis; verify with a licensed attorney before acting.