California · Evidence Code

EVID §803: The court may, and upon objection shall, exclude testimony in the form of an opinion that is based in whole or in significant part on matter that is not a proper basis for such an opinion.

What this law says, in plain English

Courts may exclude opinion testimony that relies substantially on improper sources or materials. Upon objection, courts must exclude such testimony.

Read the full statutory text

The court may, and upon objection shall, exclude testimony in the form of an opinion that is based in whole or in significant part on matter that is not a proper basis for such an opinion. In such case, the witness may, if there remains a proper basis for his opinion, then state his opinion after excluding from consideration the matter determined to be improper.

Verify at the official source: California legislative text

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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.