OJ Simpson Polygraph Test: What Really Happened (Analysis)

The Night of June 12, 1994

On the evening of June 12, 1994, Nicole Brown Simpson and Ron Goldman were found murdered outside Nicole's condominium at 875 South Bundy Drive in the Brentwood neighborhood of Los Angeles [2]Verified 25 Bizarre Facts About the O.J. Simpson Murder Trial — E! News
Confirms -24 score according to The Run of His Life by Jeffrey Toobin, and Dershowitz's comments on attorney-client privilege. Both victims had been stabbed multiple times. Nicole Brown Simpson was the ex-wife of former NFL star and media personality O.J. Simpson, and their relationship — including documented incidents of domestic violence — meant investigators quickly focused on Simpson as a primary suspect.

Physical evidence included a bloody leather glove found at Simpson's Rockingham estate that appeared to match one at the crime scene, blood drops along a pathway that DNA testing later matched to Simpson, and blood found inside Simpson's white Ford Bronco [2]Verified 25 Bizarre Facts About the O.J. Simpson Murder Trial — E! News
Confirms -24 score according to The Run of His Life by Jeffrey Toobin, and Dershowitz's comments on attorney-client privilege. Simpson had a documented history of domestic violence against Nicole, including a 1989 incident. On May 24, 1989, Simpson was sentenced to 24 months of probation, ordered to perform 120 hours of community service, and fined $470 after pleading no contest to misdemeanor domestic violence [3]Verified O.J. Simpson's Estate Rejects Kim Kardashian's Offer — E! News
Confirms Dream Team composition, Dershowitz's statements on the polygraph test, and Simpson's 1989 domestic violence plea.

The Legal Team Assembles

OJ Simpson's initial attorney was Robert Shapiro, a high-profile Los Angeles defense lawyer known for representing celebrities [2]Verified 25 Bizarre Facts About the O.J. Simpson Murder Trial — E! News
Confirms -24 score according to The Run of His Life by Jeffrey Toobin, and Dershowitz's comments on attorney-client privilege. Shapiro quickly assembled what would become known as the 'Dream Team' — a defense team that included Johnnie Cochran, Robert Kardashian, F. Lee Bailey, Barry Scheck, Peter Neufeld, Alan Dershowitz, Gerald Uelmen, Carl Douglas, and Shawn Holley [3]Verified O.J. Simpson's Estate Rejects Kim Kardashian's Offer — E! News
Confirms Dream Team composition, Dershowitz's statements on the polygraph test, and Simpson's 1989 domestic violence plea. Each brought specialized expertise: Scheck and Neufeld's pioneering work with DNA evidence through The Innocence Project, Dershowitz's constitutional law knowledge from Harvard, and Bailey's cross-examination skills [3]Verified O.J. Simpson's Estate Rejects Kim Kardashian's Offer — E! News
Confirms Dream Team composition, Dershowitz's statements on the polygraph test, and Simpson's 1989 domestic violence plea.

It was during these early days — before the famous Bronco chase on June 17, 1994 — that Shapiro made a decision that would become one of the case's most debated footnotes: he arranged for Simpson to undergo a private polygraph examination [5]Verified Simpson Friend and Lawyer Says He Flunked Polygraph — The Washington Post
Confirms Robert Kardashian told Barbara Walters on 20/20 that he was 'devastated' by the results and that Simpson claimed emotional distress caused the failure.

Why a Private Polygraph?

In criminal defense practice, ordering a private polygraph examination serves critical strategic purposes. It provides the defense attorney with confidential intelligence about the client's likely truthfulness — information that can shape the entire defense strategy. If a client passes, the attorney can pursue an aggressive innocence-based defense. If the client fails, the attorney can prepare accordingly.

Private defense polygraph tests are protected by attorney-client privilege when ordered as part of legal representation. The results cannot be compelled by the prosecution, and the defense can choose whether to disclose them. As Alan Dershowitz later noted regarding this case, the fact that the results eventually went public suggested a possible violation of attorney-client privilege [3]Verified O.J. Simpson's Estate Rejects Kim Kardashian's Offer — E! News
Confirms Dream Team composition, Dershowitz's statements on the polygraph test, and Simpson's 1989 domestic violence plea. For more on how polygraph testing serves the falsely accused, see our guide on how polygraph testing helps the falsely accused in court.

Arranging the Examination

According to multiple sources, the polygraph examination was arranged in the days immediately following the murders. The National Enquirer originally reported that Simpson was taken to the offices of lie detector examiner Edward Gelb on June 14, 1994 — just two days after the killings [6]Verified F. Lee Bailey Reveals OJ Failed Lie Detector Test / National Enquirer polygraph coverage
Confirms Bailey's testimony that Shapiro 'stopped the test and grabbed the polygraph charts,' the June 14 test date, and the -22 score on the scale. This was before the now-infamous slow-speed Bronco chase that captivated some 95 million viewers on June 17 [8]Verified O.J. Simpson Bronco Chase — CNN 25th Anniversary
Confirms approximately 95 million people watched the June 17, 1994 Bronco chase.

Shapiro selected Edward Gelb, one of the most well-known polygraph examiners in the Los Angeles area, to conduct the test [4]Verified Report: O.J. Had Flunked Lie Detector — The Spokesman-Review
Confirms Edward Gelb administered the test, score of -20, and Gelb's confirmation that -20 'definitely would indicate deception'. Gelb was a past president, executive director, and chairman of the board of the American Polygraph Association, and in 1998 earned the association's Leonarde Keeler Award for distinguished service to the polygraph profession [9]Verified Polygraph Operator Edward I. Gelb — Credentials and APA Awards
Confirms Gelb was past president, executive director, and chairman of the board of the APA; trained at Backster School; over 30,000 examinations. His selection was strategically sound — if Simpson passed, having the test administered by someone of Gelb's standing would maximize credibility.

The Critical Detail: Who Actually Administered the Test

One of the most significant and often overlooked facts about the Simpson polygraph is that Edward Gelb himself may not have actually administered the examination. According to a detailed account sourced from Lawrence Schiller and James Willwerth's American Tragedy, Gelb was in Spain at the time of the test [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score. The examination was reportedly conducted by Dennis Nellany, described as Gelb's associate and 'right-hand man' [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score.

The test took place at Gelb's mid-Wilshire offices in Los Angeles [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score. Kardashian drove Simpson to the location, where they met Shapiro and Simpson's business attorney Skip Taft [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score. This is a notable detail — the testing environment at a professional polygraph office, while better than a law firm, was still colored by the extraordinary circumstances. For context on how proper testing environments affect results, the standards published by organizations like ASTM International through their Committee E52 on Forensic Psychophysiology emphasize that the testing environment should be free from distractions [10]Verified ASTM International Committee E52 on Forensic Psychophysiology — Standards for Polygraphy
Confirms ASTM International Committee E52 has developed polygraph standards covering research, instrumentation, quality control, training, and ethics.

Simpson's Physical and Emotional State

Multiple accounts confirm that Simpson was in significant emotional distress during the test. Simpson himself described the experience afterwards: every time he heard Nicole's name, his heart would pound and he became extremely emotional [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score[5]Verified Simpson Friend and Lawyer Says He Flunked Polygraph — The Washington Post
Confirms Robert Kardashian told Barbara Walters on 20/20 that he was 'devastated' by the results and that Simpson claimed emotional distress caused the failure. He described the test as 'very hard to get through' and 'difficult, very tough' [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score.

This point is critical from a polygraph science perspective. Research has consistently shown that emotional state affects physiological responses. As the largest meta-analysis of the Comparison Question Test (CQT) found, motivation level shows a positive linear relationship with accuracy [11]Verified A Comprehensive Meta-Analysis of the Comparison Question Polygraph Test
The largest CQT meta-analysis (138 datasets) confirming strong effect size and positive relationship between motivation and accuracy. In Simpson's case, his extreme distress may have elevated physiological responses to relevant questions regardless of deception, a challenge that the examiner reportedly acknowledged [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score. The fundamental question of whether polygraph instruments measure deception directly or general physiological arousal has been a subject of ongoing research [12]Verified Evaluating Polygraphy from a Psychophysiological Perspective: A Specific-Effects Analysis
Analyzed whether polygraph responses represent specific deception-related effects or general arousal — directly relevant to the Simpson emotional state question.

Professional Background and Credentials

Edward I. Gelb was a prominent Los Angeles-based polygraph examiner who had built a decades-long reputation in the field. Since 1969, after completing training at the Backster School of Lie Detection in San Diego, Gelb claimed to have conducted in excess of 30,000 polygraph examinations [9]Verified Polygraph Operator Edward I. Gelb — Credentials and APA Awards
Confirms Gelb was past president, executive director, and chairman of the board of the APA; trained at Backster School; over 30,000 examinations. He served as past president, executive director, and chairman of the board of the American Polygraph Association (APA) — the largest professional organization for polygraph examiners in the United States [9]Verified Polygraph Operator Edward I. Gelb — Credentials and APA Awards
Confirms Gelb was past president, executive director, and chairman of the board of the APA; trained at Backster School; over 30,000 examinations.

Gelb's high-profile client list included O.J. Simpson and John and Patsy Ramsey [9]Verified Polygraph Operator Edward I. Gelb — Credentials and APA Awards
Confirms Gelb was past president, executive director, and chairman of the board of the APA; trained at Backster School; over 30,000 examinations. Along with attorney F. Lee Bailey, he appeared on a nationally syndicated television program called 'Lie Detector' [9]Verified Polygraph Operator Edward I. Gelb — Credentials and APA Awards
Confirms Gelb was past president, executive director, and chairman of the board of the APA; trained at Backster School; over 30,000 examinations. His APA leadership roles placed him at the top tier of the profession. For historical context on the evolution of polygraph instruments and the profession, see our guide on the Keeler Polygraph Model 302.

Why Gelb Was Selected

Shapiro's choice of Gelb was strategically calculated. If Simpson passed the polygraph, having the test associated with a past APA president would maximize credibility in the court of public opinion — even if results were legally inadmissible. However, this strategic calculation cut both ways. An examiner of Gelb's stature would not fabricate or manipulate results. His professional reputation meant the test would be a genuine assessment rather than a rubber-stamp exercise.

Nonetheless, since Gelb was reportedly in Spain at the time, the actual administration fell to Dennis Nellany [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score. This introduces a layer of complexity: while Nellany operated under Gelb's practice and protocols, his individual qualifications and approach are less documented in the public record.

The Varying Score Reports

The most widely cited version of the results comes from Jeffrey Toobin's 1996 book The Run of His Life, which reports that Simpson scored a minus-24 [2]Verified 25 Bizarre Facts About the O.J. Simpson Murder Trial — E! News
Confirms -24 score according to The Run of His Life by Jeffrey Toobin, and Dershowitz's comments on attorney-client privilege. Toobin's account has been the basis for most media references to the score. E! News and other outlets have consistently cited this figure [2]Verified 25 Bizarre Facts About the O.J. Simpson Murder Trial — E! News
Confirms -24 score according to The Run of His Life by Jeffrey Toobin, and Dershowitz's comments on attorney-client privilege.

However, a detailed narrative account attributed to Lawrence Schiller's American Tragedy — drawn from Kardashian's recollections — reports the score as minus-22 [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score. Separately, a 1996 report in The Spokesman-Review stated Simpson scored 'a dismal minus 20, showing definite deception' [4]Verified Report: O.J. Had Flunked Lie Detector — The Spokesman-Review
Confirms Edward Gelb administered the test, score of -20, and Gelb's confirmation that -20 'definitely would indicate deception'. Gelb himself was quoted in that report confirming that a score of minus-20 'definitely would indicate deception' [4]Verified Report: O.J. Had Flunked Lie Detector — The Spokesman-Review
Confirms Edward Gelb administered the test, score of -20, and Gelb's confirmation that -20 'definitely would indicate deception'.

During the 1997 civil trial, attorney Daniel Petrocelli asked Simpson directly whether it was true that he failed the test with a score of minus-22 [6]Verified F. Lee Bailey Reveals OJ Failed Lie Detector Test / National Enquirer polygraph coverage
Confirms Bailey's testimony that Shapiro 'stopped the test and grabbed the polygraph charts,' the June 14 test date, and the -22 score on the scale. Simpson testified that he visited Gelb's office only for a 'demonstration' of how the equipment worked and claimed he never knew the results — a statement contradicted by Kardashian [6]Verified F. Lee Bailey Reveals OJ Failed Lie Detector Test / National Enquirer polygraph coverage
Confirms Bailey's testimony that Shapiro 'stopped the test and grabbed the polygraph charts,' the June 14 test date, and the -22 score on the scale.

Regardless of whether the precise figure was -20, -22, or -24, all accounts place the score deep in the range indicating deception. As media reports noted, a score of minus-6 indicates borderline deception on the scale used, while scores of minus-20 or below indicate 'extreme deception' [6]Verified F. Lee Bailey Reveals OJ Failed Lie Detector Test / National Enquirer polygraph coverage
Confirms Bailey's testimony that Shapiro 'stopped the test and grabbed the polygraph charts,' the June 14 test date, and the -22 score on the scale. To understand how journalists cover polygraph tests and the accuracy of media reporting, our media literacy guide provides essential context.

Robert Kardashian's Confirmation

The most authoritative firsthand confirmation that Simpson failed the test came from Robert Kardashian himself. In a 1996 interview with Barbara Walters on ABC's 20/20, Kardashian said he was 'devastated by the results' of the polygraph test [5]Verified Simpson Friend and Lawyer Says He Flunked Polygraph — The Washington Post
Confirms Robert Kardashian told Barbara Walters on 20/20 that he was 'devastated' by the results and that Simpson claimed emotional distress caused the failure. He told Walters that Simpson convinced him of his innocence by explaining his failure: 'Every time I heard Nicole's name, my heart was pounding. I would get... emotional' [5]Verified Simpson Friend and Lawyer Says He Flunked Polygraph — The Washington Post
Confirms Robert Kardashian told Barbara Walters on 20/20 that he was 'devastated' by the results and that Simpson claimed emotional distress caused the failure.

Trial experts noted at the time that Kardashian's interview was the first occasion a key figure in the case directly confirmed that Simpson had failed the defense-administered test [5]Verified Simpson Friend and Lawyer Says He Flunked Polygraph — The Washington Post
Confirms Robert Kardashian told Barbara Walters on 20/20 that he was 'devastated' by the results and that Simpson claimed emotional distress caused the failure. Kardashian, who had been Simpson's close friend for 25 years and organized his defense, also revealed in the wide-ranging interview that he now had doubts about Simpson's innocence [5]Verified Simpson Friend and Lawyer Says He Flunked Polygraph — The Washington Post
Confirms Robert Kardashian told Barbara Walters on 20/20 that he was 'devastated' by the results and that Simpson claimed emotional distress caused the failure.

F. Lee Bailey's Testimony

Additional confirmation came from defense team member F. Lee Bailey during testimony in a Florida bar proceeding regarding his law license. Bailey testified that Shapiro 'stopped the test and grabbed the polygraph charts,' adding, 'I read them, and nobody else ever has' [6]Verified F. Lee Bailey Reveals OJ Failed Lie Detector Test / National Enquirer polygraph coverage
Confirms Bailey's testimony that Shapiro 'stopped the test and grabbed the polygraph charts,' the June 14 test date, and the -22 score on the scale. Bailey also maintained that it was bad practice to give Simpson the test within 48 hours of his ex-wife's murder [6]Verified F. Lee Bailey Reveals OJ Failed Lie Detector Test / National Enquirer polygraph coverage
Confirms Bailey's testimony that Shapiro 'stopped the test and grabbed the polygraph charts,' the June 14 test date, and the -22 score on the scale.

Alan Dershowitz, who primarily advised the defense team remotely from Harvard, later stated: 'There were only four in the world who knew about the lie-detector test. I was not one of them. The four people were Kardashian, who died, Bob Shapiro, O.J. Simpson and the man who conducted the lie-detector test' [3]Verified O.J. Simpson's Estate Rejects Kim Kardashian's Offer — E! News
Confirms Dream Team composition, Dershowitz's statements on the polygraph test, and Simpson's 1989 domestic violence plea. This case has parallels with other high-profile cases where polygraph evidence became publicly contested, including the Scott Peterson case and the Amber Frey polygraph analysis.

What the Defense Team Decided

One undisputed fact: the defense team chose not to disclose the polygraph results publicly and did not attempt to introduce them at trial. This speaks volumes. Defense attorneys who receive favorable polygraph results from a credible examiner have every incentive to publicize them, even if inadmissible. The suppression strongly suggests the results were unfavorable.

Shapiro himself reportedly told Simpson after hearing the results that the score was 'about as bad as you can do' [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score. According to Kardashian's account, the group vaguely agreed to wait a week and retake the test, but this never happened [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score. Shapiro collected the results in a manila envelope and instructed the group: 'This is only between us' [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score. Similar dynamics have played out in other notorious cases — for analysis of another high-profile deception case, see our article on The Jinx and Robert Durst.

How Polygraph Numerical Scoring Works

To understand the significance of Simpson's reported score, it helps to understand how polygraph scoring systems operate. The predominant methodology in the early 1990s — and still widely used today — is the Comparison Question Test (CQT). In this format, examiners compare the examinee's physiological responses to relevant questions (about the matter under investigation) with responses to comparison questions (designed to elicit a known or expected response) [11]Verified A Comprehensive Meta-Analysis of the Comparison Question Polygraph Test
The largest CQT meta-analysis (138 datasets) confirming strong effect size and positive relationship between motivation and accuracy.

The numerical scoring system, initially popularized by Cleve Backster's 7-point scoring method, involves the examiner assigning numerical values based on the relative strength of responses across physiological channels — typically respiration, electrodermal activity, and cardiovascular activity [10]Verified ASTM International Committee E52 on Forensic Psychophysiology — Standards for Polygraphy
Confirms ASTM International Committee E52 has developed polygraph standards covering research, instrumentation, quality control, training, and ethics. These scores are totaled across all channels and charts. A positive total indicates stronger responses to comparison questions (interpreted as not deceptive), while a negative total indicates stronger responses to relevant questions (interpreted as deceptive) [10]Verified ASTM International Committee E52 on Forensic Psychophysiology — Standards for Polygraphy
Confirms ASTM International Committee E52 has developed polygraph standards covering research, instrumentation, quality control, training, and ethics.

The comprehensive meta-analysis by Honts, Handler, Shaw, and Gougler (2021) — the largest ever conducted on the CQT, analyzing 138 datasets — confirmed a strong meta-analytic effect size, validating the fundamental methodology [11]Verified A Comprehensive Meta-Analysis of the Comparison Question Polygraph Test
The largest CQT meta-analysis (138 datasets) confirming strong effect size and positive relationship between motivation and accuracy. For additional research context, Vrij, Mann, and Fisher (2008) found overall CQT accuracy estimates above 85% across studies [13]Verified A Meta-Analysis of the Comparison Question Polygraph Test: Moderator Effects
Found overall CQT accuracy estimates above 85% across studies with important moderator variables.

The -6 Threshold and What Simpson's Score Means

Under the well-regarded Utah numerical scoring system, which uses a 7-position scale, scores of -6 or lower indicate deception, while scores of +6 or higher suggest truthfulness [14]Verified Inconclusive Polygraph Results — Scoring Thresholds
Confirms the Utah method uses -6 as deception threshold and +6 as truthfulness threshold for single-issue tests. Scores falling between these markers — from -5 to +5 — are classified as inconclusive [14]Verified Inconclusive Polygraph Results — Scoring Thresholds
Confirms the Utah method uses -6 as deception threshold and +6 as truthfulness threshold for single-issue tests. These mathematical boundaries reflect the probabilistic nature of polygraph science.

If Simpson's score was anywhere from -20 to -24 as various sources report, it would be far beyond the deception threshold — representing a strong, consistent physiological response pattern associated with deception across all questions and physiological channels. As Gelb himself confirmed to a reporter, a score of minus-20 'definitely would indicate deception' [4]Verified Report: O.J. Had Flunked Lie Detector — The Spokesman-Review
Confirms Edward Gelb administered the test, score of -20, and Gelb's confirmation that -20 'definitely would indicate deception'. Modern computerized scoring systems such as PolyScore (developed at Johns Hopkins University Applied Physics Laboratory), the Objective Scoring System version 3 (OSS-3, developed by the Department of Defense Polygraph Institute), and the Computerized Polygraph System (CPS, developed at the University of Utah) apply statistical analysis to physiological data and have demonstrated accuracy rates between 85-92% under laboratory conditions [15]Verified Appendix F: Computerized Scoring of Polygraph Data — National Academies Press
Confirms PolyScore and CPS computerized scoring systems, their development at Johns Hopkins and University of Utah respectively[16]Verified Modern Algorithms in Polygraph Data Analysis
Confirms OSS-3 and PolyScore accuracy rates between 85-92% under laboratory conditions. The early meta-analysis by Kircher, Horowitz, and Raskin (1988) similarly found accuracy exceeding 85% across CQT studies [17]Verified Meta-Analysis of Mock Crime Studies of the Control Question Polygraph Technique
Early meta-analysis finding accuracy exceeded 85% across CQT studies with significant moderator effects.

Emotional State and Proximity to Trauma

Regardless of guilt or innocence, the death of his ex-wife and the mother of his children was an objectively traumatic event for Simpson. The emotional turmoil of those first days — combined with awareness that he was a prime suspect — would have produced an extremely heightened physiological state in virtually anyone.

The examiner Nellany reportedly acknowledged this factor, noting that 'the test was administered close to the time of death, a very emotional time' [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score. F. Lee Bailey also maintained it was 'bad practice to give Simpson the test within 48 hours of his ex-wife's murder' [6]Verified F. Lee Bailey Reveals OJ Failed Lie Detector Test / National Enquirer polygraph coverage
Confirms Bailey's testimony that Shapiro 'stopped the test and grabbed the polygraph charts,' the June 14 test date, and the -22 score on the scale. This is a recognized challenge in polygraph science: the instrument measures physiological arousal, and extreme distress can complicate distinguishing between reactions driven by deception versus genuine trauma [12]Verified Evaluating Polygraphy from a Psychophysiological Perspective: A Specific-Effects Analysis
Analyzed whether polygraph responses represent specific deception-related effects or general arousal — directly relevant to the Simpson emotional state question.

The research by Delgado-Herrera, Reyes-Aguilar, and Giordano (2021) on ecological validity in deception tasks has highlighted that real-world conditions produce different neurological responses than laboratory settings [18]Verified What deception tasks used in the lab really do: systematic review and meta-analysis of ecological validity of fMRI deception tasks
Highlights difference between laboratory deception studies and real-world conditions — relevant to the Simpson case's emotional contamination concerns. Simpson's test, conducted under extreme real-world stress just days after a double murder, represents exactly the kind of high-stakes environment where emotional contamination of physiological data is most concerning. For more on how emotional state affects testing, see the analysis in Chris Watts' polygraph test and confession — another case where testing occurred under extreme emotional conditions.

Medication Use

Some reports indicated Simpson may have been taking medication at the time of the test, though specific medications have varied across accounts. Substances that affect the central nervous system — particularly benzodiazepines or beta-blockers — can alter the baseline physiological readings that polygraph instruments measure.

Beta-blockers can reduce cardiovascular reactivity, potentially flattening blood pressure and heart rate responses. Benzodiazepines can dampen electrodermal response. In some scenarios, medication might reduce overall physiological reactivity, making it harder for any question to produce a strong response — potentially leading to inconclusive results rather than clear deception or truthfulness calls.

Modern professional standards strongly recommend that examinees disclose all medications and that examiners evaluate whether the physiological state permits a valid examination. Organizations including the APA, the American Association of Police Polygraphists (AAPP), and ASTM International through its Committee E52 on Forensic Psychophysiology have all published detailed standards addressing these considerations [10]Verified ASTM International Committee E52 on Forensic Psychophysiology — Standards for Polygraphy
Confirms ASTM International Committee E52 has developed polygraph standards covering research, instrumentation, quality control, training, and ethics[19]Verified AAPP — American Association of Police Polygraphists
Confirms AAPP is a real professional organization dedicated to law enforcement polygraph examiners with over 1,000 members[20]Verified ASTM E2062 Standard Guide for PDD Examination Standards of Practice
Confirms ASTM publishes comprehensive polygraph examination standards through Committee E52. In 1994, these standards existed but were perhaps less uniformly codified than they are today.

The Testing Environment

While the test was conducted at Gelb's professional office rather than a law firm, the extraordinary circumstances surrounding the case created a non-standard atmosphere. Shapiro, Kardashian, and Skip Taft waited in the reception area during the examination [1]Verified American Tragedy: The Uncensored Story of the Simpson Defense (account of Kardashian's recollection)
Contains detailed account of the polygraph test scene, Nellany as examiner, Gelb being in Spain, and the -22 score. The emotional weight of the situation — a double murder investigation involving one of America's most famous athletes — would have been difficult to contain within professional boundaries.

The International Society of Polygraph Examiners' standards specify that 'the testing environment shall be free from distractions that would interfere with the examinee's ability to appropriately focus' [10]Verified ASTM International Committee E52 on Forensic Psychophysiology — Standards for Polygraphy
Confirms ASTM International Committee E52 has developed polygraph standards covering research, instrumentation, quality control, training, and ethics. Whether these conditions were fully met given the extraordinary circumstances is a legitimate question. For broader context on polygraph science in the 1970s and how testing standards have evolved through the decades, our historical analysis traces the development of professional protocols.

California Evidence Code § 351.1

Under California Evidence Code § 351.1, the results of a polygraph examination, the opinion of a polygraph examiner, or any reference to an offer to take, failure to take, or taking of a polygraph examination 'shall not be admitted into evidence in any criminal proceeding' unless all parties stipulate to the admission of such results [7]Verified California Evidence Code § 351.1
Confirms the statutory prohibition on polygraph evidence in California criminal proceedings unless all parties stipulate. This statute, effective July 12, 1983, provided a clear legal framework that made the defense team's decision to suppress the results straightforward [7]Verified California Evidence Code § 351.1
Confirms the statutory prohibition on polygraph evidence in California criminal proceedings unless all parties stipulate.

The prosecution could not compel disclosure of the private defense polygraph results, and the defense had no obligation — or incentive — to volunteer unfavorable test data. Even a reference to the fact that Simpson took a polygraph was prohibited without stipulation from both sides [7]Verified California Evidence Code § 351.1
Confirms the statutory prohibition on polygraph evidence in California criminal proceedings unless all parties stipulate.

The Kelly-Frye Standard

Beyond the statutory prohibition, California had also adopted the Kelly-Frye standard for the admissibility of scientific evidence. The landmark case People v. Kelly (1976) 17 Cal.3d 24 established that novel scientific evidence must demonstrate general acceptance in the relevant scientific community before it can be admitted [21]Verified People v. Kelly, 17 Cal.3d 24 (1976)
Confirms the Kelly-Frye standard for scientific evidence admissibility in California, referencing Frye v. United States polygraph case. The Kelly decision expressly adopted the Frye test from the 1923 federal case Frye v. United States — which itself involved the admissibility of an early polygraph test (the systolic blood pressure deception test) [21]Verified People v. Kelly, 17 Cal.3d 24 (1976)
Confirms the Kelly-Frye standard for scientific evidence admissibility in California, referencing Frye v. United States polygraph case.

Under the Kelly-Frye standard, the proponent of polygraph evidence would need to demonstrate that the methodology had gained general acceptance, present qualified expert testimony, and show that correct scientific procedures were followed [21]Verified People v. Kelly, 17 Cal.3d 24 (1976)
Confirms the Kelly-Frye standard for scientific evidence admissibility in California, referencing Frye v. United States polygraph case. This dual barrier — both statutory and case-law — meant that even if the defense had wanted to introduce favorable results, the legal hurdles would have been substantial. For a comprehensive overview of polygraph admissibility across all states, our state-by-state legal guide provides current information.

The Trial That Changed Everything

The OJ Simpson trial became one of the most closely watched legal proceedings in history. The slow-speed Bronco chase on June 17, 1994, drew approximately 95 million viewers [8]Verified O.J. Simpson Bronco Chase — CNN 25th Anniversary
Confirms approximately 95 million people watched the June 17, 1994 Bronco chase — an extraordinary figure that demonstrated the case's grip on the national consciousness. The subsequent nine-month trial drew massive daily audiences, and Simpson's acquittal on October 3, 1995, was watched by an estimated 150 million Americans [8]Verified O.J. Simpson Bronco Chase — CNN 25th Anniversary
Confirms approximately 95 million people watched the June 17, 1994 Bronco chase.

The polygraph test became one of many subplots in this sprawling drama. FX's critically acclaimed miniseries The People v. O.J. Simpson: American Crime Story dramatized the polygraph scene with Cuba Gooding Jr. as Simpson, introducing a new generation to this episode [6]Verified F. Lee Bailey Reveals OJ Failed Lie Detector Test / National Enquirer polygraph coverage
Confirms Bailey's testimony that Shapiro 'stopped the test and grabbed the polygraph charts,' the June 14 test date, and the -22 score on the scale. The show was based on Jeffrey Toobin's The Run of His Life, which provided the definitive journalistic account of the trial [2]Verified 25 Bizarre Facts About the O.J. Simpson Murder Trial — E! News
Confirms -24 score according to The Run of His Life by Jeffrey Toobin, and Dershowitz's comments on attorney-client privilege. For analysis of how other TV shows have portrayed polygraph testing, see our guides on polygraph in The Wire and Lie Detector on A&E.

How the Polygraph Story Emerged

The polygraph story leaked out gradually over several years. Initially, the defense team maintained that Simpson had not taken a full polygraph at all [6]Verified F. Lee Bailey Reveals OJ Failed Lie Detector Test / National Enquirer polygraph coverage
Confirms Bailey's testimony that Shapiro 'stopped the test and grabbed the polygraph charts,' the June 14 test date, and the -22 score on the scale. In 1996, The Spokesman-Review reported on leaked details of the test, citing a score of -20 and Gelb's confirmation that such a score 'definitely would indicate deception' [4]Verified Report: O.J. Had Flunked Lie Detector — The Spokesman-Review
Confirms Edward Gelb administered the test, score of -20, and Gelb's confirmation that -20 'definitely would indicate deception'.

Kardashian's 1996 20/20 interview with Barbara Walters marked the first time a key insider directly confirmed the failure [5]Verified Simpson Friend and Lawyer Says He Flunked Polygraph — The Washington Post
Confirms Robert Kardashian told Barbara Walters on 20/20 that he was 'devastated' by the results and that Simpson claimed emotional distress caused the failure. F. Lee Bailey's testimony during Florida bar proceedings added further detail about Shapiro's intervention [6]Verified F. Lee Bailey Reveals OJ Failed Lie Detector Test / National Enquirer polygraph coverage
Confirms Bailey's testimony that Shapiro 'stopped the test and grabbed the polygraph charts,' the June 14 test date, and the -22 score on the scale. Dershowitz's later comments suggested the leak may have constituted a breach of attorney-client privilege [3]Verified O.J. Simpson's Estate Rejects Kim Kardashian's Offer — E! News
Confirms Dream Team composition, Dershowitz's statements on the polygraph test, and Simpson's 1989 domestic violence plea.

The case highlights the complex relationship between polygraph testing and media coverage. As our media literacy guide on how journalists cover polygraph tests explores, the interplay between confidential test results and public disclosure can significantly shape narratives. Similar dynamics have played out in the Johnny Depp-Amber Heard polygraph debate and other high-profile cases.

The Value of Private Defense Polygraph Testing

The Simpson case illustrates both the potential and the risks of private defense polygraph examinations. When properly administered under optimal conditions, a defense polygraph can be an invaluable intelligence tool. A favorable result gives the attorney confidence to pursue an innocence-based strategy. An unfavorable result — protected by privilege — allows the attorney to adjust strategy without exposure.

However, the Simpson case also demonstrates that timing matters enormously. Testing a client who is emotionally traumatized, potentially medicated, and only days removed from the event under investigation introduces significant reliability concerns. Modern best practices recommend waiting until the examinee has stabilized emotionally and any medication effects can be properly accounted for [10]Verified ASTM International Committee E52 on Forensic Psychophysiology — Standards for Polygraphy
Confirms ASTM International Committee E52 has developed polygraph standards covering research, instrumentation, quality control, training, and ethics. For attorneys considering polygraph evidence in immigration or other proceedings, our guide to polygraph evidence in immigration court provides specialized guidance.

Modern Polygraph Standards vs. 1994 Practices

Polygraph testing has advanced significantly since 1994. Modern computerized scoring systems — including PolyScore, OSS-3, CPS, and newer deep-learning-based algorithms — reduce examiner subjectivity and improve consistency [15]Verified Appendix F: Computerized Scoring of Polygraph Data — National Academies Press
Confirms PolyScore and CPS computerized scoring systems, their development at Johns Hopkins and University of Utah respectively[16]Verified Modern Algorithms in Polygraph Data Analysis
Confirms OSS-3 and PolyScore accuracy rates between 85-92% under laboratory conditions. The APA has published comprehensive standards of practice, and ASTM International's Committee E52 has developed standards covering research (E1954), quality control (E2031), instrumentation calibration (E2063), examination standards (E2062), and ethics (E2065) [10]Verified ASTM International Committee E52 on Forensic Psychophysiology — Standards for Polygraphy
Confirms ASTM International Committee E52 has developed polygraph standards covering research, instrumentation, quality control, training, and ethics[20]Verified ASTM E2062 Standard Guide for PDD Examination Standards of Practice
Confirms ASTM publishes comprehensive polygraph examination standards through Committee E52.

The development of these standards was partly driven by court decisions that noted the absence of universal protocols in the polygraph profession [10]Verified ASTM International Committee E52 on Forensic Psychophysiology — Standards for Polygraphy
Confirms ASTM International Committee E52 has developed polygraph standards covering research, instrumentation, quality control, training, and ethics. Today, validated testing methods are paired with specific scoring rules, and examiners are expected to document any conditions that may affect result validity [10]Verified ASTM International Committee E52 on Forensic Psychophysiology — Standards for Polygraphy
Confirms ASTM International Committee E52 has developed polygraph standards covering research, instrumentation, quality control, training, and ethics. The Concealed Information Test (CIT), an alternative methodology, has demonstrated particularly low false positive rates — as low as 4.1% according to Elaad's meta-analysis [22]Verified Meta-Analysis of CIT Laboratory Studies
Found the CIT false positive rate was only 4.1%, establishing exceptionally low false positive rates for this methodology. The P300-based CIT approach has also shown promise, with Knappe, Ullsperger, and Kirschner (2025) finding a large mean effect size [23]Verified Decoding Deception with the P300: A Meta-Analysis of the Concealed Information Test
Found a large mean effect size of 1.59 for the P300-based CIT across 54 studies.

For a broader perspective on how polygraph science has evolved through the decades, our articles on polygraph in the 1960s, the 1970s NAS debate, and the 1980s workplace testing era trace this important history. The work of August Vollmer in Berkeley laid the groundwork for modern forensic polygraphy.