Are Polygraph Tests Admissible in California Criminal Trials?
In California, polygraph test results are generally not admissible in criminal trials.
Under California law, polygraph evidence can be admitted only if both the prosecution and the defense agree in advance to admit it.
Without mutual agreement, the following are inadmissible:
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Polygraph test results
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The fact that a polygraph was offered
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The fact that a polygraph was taken
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The refusal to take a polygraph
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The opinion of a polygraph examiner
Because this agreement rarely happens, polygraphs are almost never presented to a jury in California criminal cases.
Your best hope for a favorable outcome is with an experienced criminal defense attorney at Eisner Gorin LLP. To schedule a consultation, call (818) 781-1570 or contact us here.
What Is a Polygraph Test?
A polygraph, often called a lie detector test, is a device that measures physiological responses such as:
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Heart rate
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Blood pressure
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Breathing patterns
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Perspiration
The theory is that deceptive answers produce measurable biological changes.
However, polygraphs do not directly measure truthfulness. They measure stress responses, which can be influenced by anxiety, fear, confusion, or other emotional reactions unrelated to deception.
Why Are Polygraphs Restricted in California Courts?
There are two primary reasons polygraph evidence is restricted:
Reliability Concerns
Courts have long questioned the scientific reliability of polygraph testing.
Common concerns include:
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Subjective interpretation by the examiner
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False positives, where truthful individuals appear deceptive
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False negatives, where deceptive individuals appear truthful
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Countermeasures used to manipulate results
Because polygraph results depend heavily on interpretation, courts consider them insufficiently reliable for jury trials.
Constitutional Protections
Polygraph examinations can raise serious constitutional concerns.
During a polygraph:
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You may be asked incriminating questions
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Statements made during the test can be used against you
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The presence of counsel is limited
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Silence or refusal to answer may be interpreted negatively
Your Fifth Amendment right to remain silent and Sixth Amendment right to counsel must be protected at all times.
Even if the test results are inadmissible, statements you make during questioning may still be admissible.
Can Police Force You to Take a Polygraph?
No.
In California, law enforcement cannot force a suspect or witness to take a polygraph test.
You have the absolute right to refuse.
In most cases, experienced criminal defense attorneys advise clients not to submit to a police-administered polygraph without legal counsel.
When Can Polygraphs Be Used in California Cases?
Although polygraphs are generally inadmissible at trial, they may be used in limited situations.
Plea Negotiations
Polygraph results may be used informally during negotiations between defense and prosecution to assess credibility.
Pretrial Hearings
If both parties agree, results may be admitted during certain pretrial proceedings.
Investigative Tool
Law enforcement may use polygraphs during investigations to:
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Narrow suspect pools
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Verify statements
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Guide investigative strategy
However, results are typically not presented to juries.
Private Polygraphs
A defendant may voluntarily take a private polygraph examination.
If the results are favorable:
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They may be presented to the prosecutor
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They may assist in pre-filing intervention
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They may help persuade prosecutors to reject charges
If unfavorable, the results can remain confidential.
Parole and Post-Conviction Monitoring
Polygraphs may be used in:
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Parole proceedings
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Sex offender supervision
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Treatment compliance monitoring
These uses occur outside of jury trials.
What Happens If You Refuse a Polygraph?
Your refusal cannot be used as evidence against you unless both sides agreed beforehand to admit that fact.
Refusal alone does not imply guilt.
However, investigators may continue pursuing other evidence.
Can Polygraphs Help Get Charges Dismissed?
In some cases, a favorable private polygraph may:
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Strengthen negotiation leverage
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Support a pre-filing rejection request
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Encourage prosecutors to reevaluate evidence
While not dispositive, it may serve as a strategic tool when used properly.
Polygraphs should never be taken casually. Timing and legal strategy are critical.
Frequently Asked Questions
Are polygraph results ever admitted in California jury trials?
Only if both prosecution and defense agree in advance. Otherwise, they are excluded.
Can statements made during a polygraph be used in court?
Yes. While test results may be inadmissible, your statements during questioning can often be introduced as evidence.
Should I take a polygraph to prove my innocence?
You should consult a criminal defense attorney before agreeing to any polygraph examination.
Is a private polygraph different from a police polygraph?
Yes. A private polygraph is arranged independently and results may remain confidential unless you choose to disclose them.
Can refusing a polygraph make me look guilty?
Legally, refusal cannot be used against you unless agreed in advance. Investigators may still draw their own conclusions.
Strategic Considerations Before Taking a Polygraph
Before agreeing to any polygraph examination, consider:
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The strength of the prosecution's case
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The risks of making statements
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The reliability of the examiner
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Whether pre-filing intervention is possible
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Whether negotiation leverage exists
Even truthful individuals can “fail” polygraphs due to stress.
The decision should always be made with experienced legal guidance.
Under Investigation in California?
If law enforcement asks you to take a polygraph, consult a criminal defense attorney immediately.
Even though the results may not be admissible in court, anything you say can be used against you.
An experienced California criminal defense lawyer can evaluate whether:
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Refusal is appropriate
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A private polygraph may be beneficial
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Pre-filing intervention is possible
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An early negotiation strategy should be implemented
Protecting your rights early can dramatically affect the outcome of your case.
Contact a California criminal defense attorney to discuss your situation confidentially before submitting to any polygraph examination.
Eisner Gorin LLP is here to help. Schedule your consultation at (818) 781-1570 or contact us here. Our law firm is based in Los Angeles.
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