Los Angeles Lie Detector Test Lawyer

A modern polygraph is a multi-channel physiological recorder that tracks respiration, galvanic skin response (sweat gland activity), blood-volume pulse, and, in most professional models, peripheral blood pressure. As part of the Los Angeles criminal process, these tests may be used during investigations or as evidence in negotiations. By monitoring these autonomic functions while the subject answers a carefully scripted series of questions, the examiner looks for patterns that may correlate with deception.

The underlying premise is that a person who is consciously lying experiences measurable stress that “leaks” through bodily changes too subtle for the naked eye, insights that a skilled Los Angeles lie detector test lawyer can help interpret and challenge in court.

Laboratory studies show accuracy rates that range from the low 60s to the mid-90s, depending on the methodology and the examiner’s skill. Real-world field studies, however, consistently report error rates high enough to raise due-process concerns, primarily false positives that label truthful subjects as liars. Because the polygraph measures generalized arousal, it can be triggered by anxiety, embarrassment, trauma, lack of sleep, caffeine, or certain medications. For these reasons, most scientific bodies (including the National Academy of Sciences) classify the technology as “not sufficiently reliable for evidentiary use.”

California’s stance is codified in Evidence Code § 351.1. The statute places a categorical ban on admitting “the results of a polygraph examination, the opinion of a polygraph examiner, or any reference to an offer to take, failure to take, or the taking of a polygraph examination” in any criminal proceeding, unless every party first signs a written stipulation. Even then, the trial judge retains discretion to exclude the evidence for undue prejudice or lack of probative value.

The Legislature’s policy choice tracks decades of case law. In People v. Kelly (1976), the California Supreme Court adopted the now-famous three-prong Kelly/Frye reliability test for novel scientific evidence. Polygraph technology repeatedly failed that test because it lacked “general acceptance” in the scientific community. More recently, the Court reaffirmed the statutory exclusion in People v. Wilkinson (2004), describing § 351.1 as a “categorical prohibition.”

As a result, a jury rarely sees polygraph charts, examiner opinions, or even hears that a test was offered, unless the defense and prosecution both decide that the results serve their strategic interests. A skilled Los Angeles lie detector test lawyer can navigate these legal barriers, though prosecutors often decline to stipulate, effectively blocking admission.

Because courtroom admissibility is so restricted, the real value of a polygraph in California is pretrial leverage:

• Pre-file investigations. A well-conducted private examination, administered before charges are filed, can persuade detectives or deputy district attorneys to drop an inquiry or file lesser counts. Prosecutors know the jury will never hear about the test, but they also understand that a “truthful” chart can undercut probable cause.
• Charging and plea negotiations. Even after arraignment, an exculpatory polygraph report placed in the prosecutor’s file may prompt better offers, alternative diversion options, or outright dismissal. Many district attorney offices have written guidelines that allow the handling deputy to consider un-stipulated defense polygraphs when exercising prosecutorial discretion.
• Witness credibility vetting. Defense counsel sometimes administers a polygraph test to key defense witnesses to gauge the risk before putting them on the stand.
• Sentencing mitigation. Though test results themselves are excluded, statements the client makes during the post-test interview can be admissible as spontaneous declarations or as evidence of remorse, if they are helpful.

Quality control is critical. California does not have a statewide licensing board for polygraph examiners, resulting in widely varying credentials. Attorney Michael Kraut works exclusively with examiners who:

• Are they former federal or major-agency examiners (e.g., FBI, Secret Service, DoD)?
• Trained at an American Polygraph Association-accredited school;
• Use computerized Lafayette or Stoelting instruments with validated scoring algorithms; and
• Audio- and video-record every session to preserve the chain of custody and deter misconduct.

Using a reputable examiner and documenting every step dramatically increases the test’s persuasive power when negotiating with the prosecution, predominantly when guided by an experienced lie detector test lawyer.

• Pre-test interview. The examiner collects the examinee's personal history, medical issues, medication lists, and their account of the events. This stage typically runs 45–90 minutes and forms the foundation for relevant and comparison questions.
• Question review. All questions are read verbatim to the examinee before any sensors are attached. Surprises are unethical and invalidate the procedure.
• Data collection. The examinee is connected to sensors, and the examiner administers multiple charts (usually three) with structured breaks in between.
• Post-test interview and scoring. After the sensors are removed, the examiner scores the charts using a combination of numerical evaluation and computer algorithms. If the charts show “no deception indicated,” the examiner may conduct an additional interview to lock in exculpatory statements, which are transcribed for counsel.

The entire appointment lasts two to three hours. It is typically conducted in a neutral, distraction-free office, never in a jail or police facility, which can heighten anxiety and distort results.

Law enforcement may invite a suspect to take a “quick polygraph to clear things up.” Declining that invitation cannot be mentioned at trial, but statements made during the test are admissible even if the charts are not. A seasoned defense attorney will almost always advise clients not to submit to a police-controlled exam because:

• The examiner works for the state.
• The questioning is designed to elicit admissions, and
• The prosecution can still use any damaging statements under traditional hearsay exceptions.

If a client believes a polygraph test could be helpful, a lie detector test lawyer should arrange a private, defense-directed test first. Only if the defense is satisfied with the result should it consider stipulating with the prosecutor for courtroom admission.

As a former Deputy District Attorney, Michael Kraut understands exactly how prosecutors evaluate evidence. When appropriate, our firm uses polygraph examinations to:

• Head off charges. We have persuaded filing deputies to reject felony complaints after presenting strong polygraph charts together with corroborating documentary evidence.
• Secure diversion. In one recent assault investigation, a favorable exam helped convince the city attorney to divert the case into an informal resolution, saving the client from any criminal record.
• Impeach shaky accusations. In a domestic-violence matter, we arranged dueling polygraphs for the complainant and the accused; the differing outcomes exposed credibility problems that led to dismissal on the morning of trial.

Because the results are rarely admissible, timing and presentation are everything. We coordinate closely with retained experts to ensure the district attorney receives a concise, professionally packaged report that highlights every reliability safeguard.

Polygraph examinations can be powerful investigative and negotiating tools, but only when deployed by counsel who understands the technology’s scientific limitations and California’s evidentiary complexities. At Kraut Law Group Criminal & DUI Lawyers, we draw on decades of prosecution and defense experience, and partnerships with the region’s most respected polygraph examiners, to craft strategic testing plans that protect your rights and advance your defense.

If you are under investigation or have already been charged, please contact our Los Angeles office 24/7 for a confidential case evaluation.